# AQS Data Dictionary

The AQS Data Dictionary describes the fields typically encountered by AQS users and are listed in alphabetical order. Field definitions and calculation algorithms are provided as appropriate.

The fields are presented in alphabetic order and descriptions include:

• A narrative describing the field, including its uses;
• Any rules of value assignment, including algorithms and formulas.

The prior PDF version of the Data Dictionary will no longer be updated. We will make the PDF version available until all equivalent information is included here.

In many instances, one field will be related to another and may reference the "primary" field which may have a more complete definition. In this case the first letters of the referenced field will be captialized (like a Proper Noun).

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## 1 Point QC Bias Estimate

One Point Quality Control Check Bias upper bound

## 1 Point QC Bias Sign

One Point Quality Control Check Bias Sign

## 1 Point QC Check Summary Begin Date

The greatest of: January 1 of the summary year; Earliest date falling within a sample period for the monitor and summary year; Earliest date falling within the PQAO assignment for the monitor and summary year.

## 1 Point QC Check Summary End Date

The earliest of: December 31 of the summary year; Latest date falling within a sample period for the monitor and summary year; Latest date falling within the PQAO assignment for the monitor and summary year; Calendar date that the summary is retrieved.

## 1 Point QC Data Percent Complete

The smallest of: (100 * Num_Observations / Num_Required) OR 100.

## 1 Point QC Required Checks

The number of two week periods falling completely within a sample period and the PQAO assignment for the monitor for the summary year.

## 10th Percentile

The sample value in the summarized sample set where 10% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## 25th Percentile

The sample value in the summarized sample set where 25% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## 3 Month Rolling Average Maximum Month

The earliest month (if multiple) in the summarized year with the maximum 3-month rolling average

## 50th Percentile

The sample value in the summarized sample set where 50% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## 75th Percentile

The sample value in the summarized sample set where 75% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## 90th Percentile

The sample value in the summarized sample set where 90% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## 95th Percentile

The sample value in the summarized sample set where 95% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## 98th Percentile

The sample value in the summarized sample set where 98% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## 98th Percentile Completeness Indicator

Flag (e.g. Y, N) to indicate that the PM 98th percentile is valid as per 40 CFR Part 50 Appendix N.

### Value Assignment

Set to Y (Yes, valid value) if:
• All 4 site-level quarterly summaries are present, and
• One of the following is true:
• All 4 quarters are 75% complete, or
• Annual 98th percentile value greater than the level of the 24-hour standard.

## 99th Percentile

The sample value in the summarized sample set where 99% of the values in that set are less than or equal to it. (For ozone, based on valid daily maxima; for PM2.5, based on seasonal and non-seasonal algorithms.)

## Accuracy Audit ID Number

A sequentially assigned number used to identify a unique measurement data group for a monitor on a specific date.

## Accuracy Audit Scale

The number of digits to the right of the decimal reported for the accuracy audit data.

## Accuracy Data Date

The date the collected accuracy data applies to.

## Accuracy Data Type

The type of data the collected accuracy data represents.

## Accuracy Type

Defines the ACT_ACC_TYPE (if Accuracy data) to filter by to determine the data entered for the given assessment. Not used for Precision data.

## Action Indicator for Transaction

Indicator for Insert, Update, Delete, or Replace data manipulation action.

## Actual Days Greater than the Standard

The number of days during the year that exceeded the standard (as opposed to estimated days).

## Actual Sample Date

For a precision pair, the date that the monitor with the known sample concentration collected a sample.

## Actual Scale

For a precision pair, the number of digits to the right of the decimal place that the Actual Value is reported.

## Actual Value

For a precision pair, the sample value from the monitor with the known concentration (the "truth" value).

## Agency

The name of the agency responsible for some aspect of AQS data handling.

## Agency Code

The code representing the agency responsible for some aspect of AQS data handling.

## Agency Role

The role the agency performs with respect to AQS data handling (e.g., collecting, reporting, etc.).

## Agency Role Begin Date

The date on which the agency began performance of the role for the monitor. For the role of reporting, it also indicates the date that precision and accuracy data applies to the agency as reporting organization.

## Agency Role End Date

The date on which the agency ended a period of performance of the role for the monitor. For the role of reporting, it also indicates the last date that precision and accuracy data applies to the agency as reporting organization.

## Agency Type

The full description of the type of agency: state, federal, lab, contractor, etc.

## Agency Type Code

A code representing the type of agency: state, federal, lab, contractor, etc.

The threshold at which a public health alert is triggered.

## Alternate Method Detection Limit

The method detectable limit (MDL) defined for the sample by the QA agency, which supersedes the EPA-defined method detectable limit for the designated methodology.

## Analysis Audits Submitted

Number of submitted analysis audits.

## Analyzing Agency

The name of the agency assigned as "Analyzing" for the monitor reporting data.

## Analyzing Agency Code

The code of the agency assigned as "Analyzing" for the monitor reporting data.

## Analyzing Lab Code

The AQS Agency code of the laboratory performing lead filter analyses for the PQAO. (If there are multiple labs, this field is NULL.)

## Annual Creditable Days

The number of creditable days during a reported site-parameter-year for the Combined Site Sample Value Listing request.

## Annual Standard

A description of the annual NAAQS standard.

## Annual Standard ID

The AQS tracking number for the annual NAAQS standard.

## Annual Standard Level

The concentration level used to compare the annual design value against.

## Annual Statistic Name

The form of the annual standard (the statistic calculated to compare against the standard).

## Annual Weighted Mean

The weighted arithmetic mean for a reported site-parameter-year for the Combined Site Sample Value Listing request.

## Appendix A Indicator

Indicator defining if the record is subject to 40 CFR Part 58 Appendix A Requirements.

## Applicable Standards Indicator

An indication of whether the data from a monitor in a monitor planning area should be compared to either the short-term or annual National Ambient Air Quality Standards (NAAQS), or both.

## AQCR

The name of Air Quality Control Region where the site is located.

## AQCR Code

The code of Air Quality Control Region where the site is located.

## AQI

The Air Quality Index for the day for the pollutant, if applicable. The air quality index is a unitless measure of the amount of pollutant that can be used to relate the pollutant to the healthy levels and indicate possible health concerns with elevated levels. The Air Quality Index (AQI) is a measure for reporting daily air quality. It focuses on health effects that may be experienced within a few hours or days after breathing polluted air. AQI is calculated for the following major air pollutants regulated by the Clean Air Act: Ozone, PM 2.5, PM 10, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The AQI is a mapping from pollutant concentrations to the common index. The index is based on defining seven levels of concentration/index values that are classified as follows:

• Good (with AQI values from 0 to 50),
• Moderate (with AQI values from 51 to 100),
• Unhealthy for Sensitive Groups (with AQI values from 101 to 150),
• Unhealthy (with AQI values from 151 to 200),
• Very Unhealthy (with AQI values from 201 to 300),
• Hazardous (with AQI values above 301).
The upper and lower bounds of each AQI level classification are called “breakpoints” for the level. The EPA defines specific pollutant concentrations to be associated with each breakpoint; e.g. for Ozone, the “Moderate” classification level has the concentration of 0.060 ppm associated with its lower AQI value of 50, and the concentration of 0.075 associated with its higher AQI value of 100. AQI values in this concentration range are then computed by linear interpolation.

### Value Assignment

$$AQI = \left( \left( \frac{I_{High} - I_{Low}} {BP_{High} - BP_{Low}} \right) \times (Conc - BP_{Low} ) \right) + I_{Low}$$

Where:
$$Conc =$$ The concentration of the pollutant
$$I_{High} =$$ The AQI value of the upper break point of the level
$$I_{Low} =$$ The AQI value of the lower break point of the level
$$BP_{High} =$$ The concentration associated with the upper breakpoint of the level
$$BP_{Low} =$$ The concentration associated with the lower breakpoint of the level

## AQI Category

The name of the category the numerical AQI falls within.

## AQI Date

The Date the AQI value applies to.

## AQI Defining Site

Site ID for site with maximum AQI value over the selected geographic area.

## Arithmetic Mean (3 Month)

The measure of central tendency obtained from the sum of monthly means in the 3-month rolling data set divided by the number of values that comprise the sum for 3 month rolling data set. The sum of values only adds the values with the appropriate flagging and concurrence for the exceptional data type.

### Value Assignment

$$u = \frac {1}{n} {\sum_{i=1}^n X_i}$$

Where:
$$u =$$ mean value
$$n =$$ valid monthly means in the quarter
$$X =$$ monthly mean

## Arithmetic Mean (Annual)

The measure of central tendency obtained from the sum of the observed pollutant data values or National Ambient Air Quality Standards (NAAQS) averages in the yearly data set divided by the number of values that comprise the sum for the yearly data set. For criteria pollutants, the sum of values only adds the values with the appropriate flagging and concurrence for the exceptional data type.

### Value Assignment

#### Ozone, SO2, and NO2

$$u = \frac {1}{v} {\sum_{i=1}^v d_i}$$

Where:
$$u =$$ mean value
$$d_i =$$ valid daily maximum occurring in the effective monitoring season
$$v =$$count of valid days

#### All Others

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

## Arithmetic Mean (Daily)

The measure of central tendency obtained from the sum of the observed pollutant data values or National Ambient Air Quality Standards (NAAQS) averages in the daily data set divided by the number of values that comprise the sum for the daily data set. For criteria pollutants, the sum of values only adds the values with the appropriate flagging and concurrence for the exceptional data type.

### Value Assignment

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

## Arithmetic Mean (Monthly)

The measure of central tendency obtained from the sum of Site Daily values in the monthly data set divided by the number of values that comprise the sum for monthly data set. The sum of values only adds the values with the appropriate flagging and concurrence for the exceptional data type.

### Value Assignment

$$u = \frac {1}{v} {\sum_{i=1}^v d_i}$$

Where:
$$u =$$ mean value
$$d_i =$$ valid daily values in the month
$$v =$$count of valid days in the month

## Arithmetic Mean (NAAQS Period)

The measure of central tendency obtained from the sum of the observed pollutant data values in National Ambient Air Quality Standards (NAAQS) averaging interval divided by the number of values that comprise the sum for the NAAQS averaging interval. For criteria pollutants, the sum of values only adds the values with the appropriate flagging and concurrence for the exceptional data type.

### Value Assignment

#### 8-Hour Ozone Complete

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

#### 8-Hour Ozone Incomplete

$$u = \frac {1}{8} { \left( {\sum_{i=1}^n S_i} + ( (8-n)*h ) \right) }$$

Where:
$$u =$$ mean value
$$s_i =$$ 1-hour (sample) value
$$h =$$ 1/2 the method detection limit (MDL) $$n =$$number of 1-hour (sample) values

#### 8-Hour CO

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

#### 3-Hour SO2 Complete

$$u = \frac {1}{3} {\sum_{i=1}^3 s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement

#### 3-Hour SO2 Incomplete

$$u = \frac {1}{3} {\sum_{i=1}^3 s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement

#### 24-Hour SO2 Complete

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

#### 24-Hour SO2 Incomplete

$$u = \frac {1}{24} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement

#### 24-Hour PM10 Complete

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

#### 24-Hour PM10 Incomplete

$$u = \frac {1}{24} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement

#### 24-Hour PM2.5 Complete

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

#### 24-Hour PM2.5 Incomplete

$$u = \frac {1}{24} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement

## Arithmetic Mean (Quarterly)

The measure of central tendency obtained from the sum of the observed pollutant data values in the quarterly data set divided by the number of values that comprise the sum for the quarterly data set. For criteria pollutants, the sum of values only adds the values with the appropriate flagging and concurrence for the exceptional data type.

### Value Assignment

#### Hourly and NAAQS Durations

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

#### Site Level PM2.5

$$u = \frac {1}{n} {\sum_{i=1}^n s_i}$$

Where:
$$u =$$ mean value
$$s_i =$$ sample measurement
$$n =$$number of samples

## Arithmetic Mean Completeness Indicator

Flag (e.g. Y, N) to indicate that the annual mean is valid as per 40 CFR Part 50 Appendix N.

## As of Date

This is the date the data was extracted from an EPA system. This is provided so that updated information can be queried by using a "date of last change" after the last "as of date".

## Assessment Concentration

The value of the known gas standard concentration.

## Assessment Date

Date that the QA assessment was performed

## Assessment Flow Rate

The flow rate of the flow transfer standard.

## Assessment Frequency

Defines the number of times within the FREQ_TYPE the assessment is required to be performed.

## Assessment Frequency Type

Defines how long of a time period the assessment is evaluated.

## Assessment Level Number

For multi-level assessments, an indicator of which assessment level is represented by the field and control measurements.

## Assessment Number

A unique number associated with an assessment performed at a site on a given day. Value should be "1" unless additional same assessments are performed.

## Assessment Number Per Interval

Defines the number of samples that are required with each instances of the assessment.

## Assessment Observation Count Type

Defines how to determine the total number of observations for the ASSESSMENT.

## Assessment Source Table

Defines the table where the given ASSESSMENT information may be obtained.

## Assessment Source Type

Defines the AUC_AUDIT_CLASS (if Accuracy data) or PRECISION_TYPE (if Precision) to filter by to determine the data entered for the given assessment.

## Assessment Type

The QA Assessment Type. "Speciation Flow Rate Ver", "Speciation Flow Rate Audit", "PMc Flow Rate V", or "PMc Semi Annual Flow Rate Audit"

## Assessment Value

The flow rate of the flow transfer standard

## Audit Action Index

AQS internal index for audit actions

## Audit Class

Description of the class of audit taken at the monitor.

## Audit Date

The date the audit was performed.

## Audit ID

The audit ID of the legacy monitor-level lead analysis audit.

## Audit Level

A number identifying a regulatory-specified concentration range for the Parameter, or, when there is no level defined, a sequential identifier use to differentiate multiple value pairs in an accuracy audit.

## Audit Level Index

AQS internal index of the audit levels

## Audit Reference Sample ID

The unique identity (ID) number of the reference sample used to challenge the instrument.

## Audit Scheduled Date

The initial date that the performance audit was scheduled.

## Audit Type

Description of who performed the audit and how the audit standard was certified.

## Auditing Agency

The name of the agency assigned as "Auditing" for the monitor reporting data.

## Auditing Agency Code

The code of the agency assigned as "Auditing" for the monitor reporting data.

## Authoritative standard ID

Unique ID for Authoritative standard.

## Authoritative Standard Level

Primary EPA standard is Level 1, those validated against it are level 2, and those validated against level 2 standards are level 3.

## Authoritative Standard Value 1-10

For ozone SRP quailty assurance assessments, the measurement from authoritative standard instrument. There are 10 fields available, enter values beginning in the first.

## Average Percent Difference

The average of the Percent Differences (d).

## Bias Estimate

The bias estimate made by evaluating the mean of the absolute values of the percent differences.

## Bias Sign

Sign (+, -, or +/-) of the bias of the percent differences.

## Blank Date

The date on which the blank process began.

## Blank Datetime

The date and time at which the blank process began.

## Blank Scale

The number of digits beyond the decimal place used in reporting the blank data.

## Blank Time

The time at which the blank process began.

## Blank Type

The type of blank being reported (Trip, Field, Lab, etc.)

## Blank Value

The measured value from the blank in the standard units of measure for the parameter.

## Calendar Month Name

The name of the calendar month.

## Calendar Month Number

The number of the calendar month (within the year).

## Calendar Quarter

The number of the calendar quarter.

## Calendar Year

The year represented by the data.

## CBSA

The name of the core based statistical area (metropolitan area) where the monitoring site is located.

## CBSA Code

The code of the core based statistical area (metropolitan area) where the monitoring site is located.

## CBSA Short Name

The short version of the OMB-assigned title for the core-based statistical area (CBSA).

## Certification Indicator

An indication whether the completeness and accuracy of the information on the annual summary record has been certified by the submitter. Certified means the submitter has certified the data (due May 01 the year after collection). Certification not required means that the parameter does not require certification or the deadline has not yet passed. Uncertified (past due) means that certification is required but is overdue. Requested but not yet concurred means the submitter has completed the process, but EPA has not yet acted to certify the data. Requested but denied means the submitter has completed the process, but EPA has denied the request for cause. Was Certified but data changed means the data was certified but data was replaced and the process has not been repeated.

## Certification Indicator Flag

A Flag indicating the official certification status of the monitor-year, as assigned by the applicable regional office user.

## Certification Year

Year for which the data is being certified.

## Certifying Agency

The name of the agency assigned as "Certifying" for the monitor reporting data.

## City

The name of the city where the monitoring site is located. This represents the legal incorporated boundaries of cities and not urban areas.

## City Code

The census city code within whose incorporated boundary the monitor resides.

## Class 1 Area Code

The code of the Class One Area within which the site is located.

## Class 1 Area Name

The Class One Area within which the site is located.

## Coefficient of Variation

Coefficient of Variation of the Percent Differences (d).

## Coefficient of Variation Upper Bound

90% Upper bound on Coefficient of Variance

## Collecting Agency

The name of the agency assigned as "Collecting" for the monitor reporting data.

## Collecting Agency Code

The code of the agency assigned as "Collecting" for the monitor reporting data.

## Collection Date

The date for which the monitor's sample data or NAAQS averages are summarized.

## Collocated Audits Performed

Number of sites actually with collocated data for year

## Collocated Audits Required

The number of collocated audits that are required to be performed. Determined as CEIL(0.2 * Monitor_Count)

## Collocated Monitor POC

The Parameter Occurrence Code (POC) of the duplicate sampler. Only applies to collocated data where the duplicate value is a recorded daily raw data point.

## Collocated Site Count

The number of sites that are collocated within the network. This value is only computed for SUMMARY rows.

## Collocated Site Percent Requirement

The percentage of the required sites to be collocated within the network. This value is only computed for SUMMARY rows.

## Collocated Sites Required

The number of collocated audits required. Calculated for PM as 15% of total sites. Calculated for Lead as If there are 5 or fewer lead sites in the PQAO measuring the parameter in a given year then 4 Lead (PM10 or TSP) collocated audits are required; if there more than 5 lead sites in the PQAO within the year, the number required is 6.

## Collocation Begin Date

Date on which monitor QA collocation began.

## Collocation End Date

Date on which monitor QA collocation ended

## Collocation Percent

The smallest of the following quantities: 100 OR 100 * Num_Actual_colloc/Num_Colloc_Req

## Collocation Percent Complete

Monitor-Level Collocation percent completeness

## Collocation PQAO Status

Status of PQAO-Level Collocation Summary

## Collocation Precision

Monitor-Level Collocation CV upper bound (90%)

## Combined Bias Estimate

Combined bias estimate across all levels.

## Combined Bias Sign

Sign for combined bias estimate.

## Combined Percent Complete

Completeness across both levels

## Combined Percent Difference

Median relative percent difference across all levels

## Comment

A comment associated with the site, monitor, or sample.

## Comment Sequence Number

The sequential identification number used to distinguish multiple comment entries.

## Community Monitoring Zone Number

A sequential number assigned to an optional averaging area with an established, defined boundary within a monitor planning area that has relatively uniform concentration of annual PM-2.5. Community monitoring zones do not cross geographical lines.

## Compass Sector

Short version of one of the 16 standard compass directions/points. For example, N, NW, NNW, etc.

## Complete Quarter Count

The number of quarterly summaries, with corresponding pollutant standard and exceptional data type, where the summary criterion is met.

### Value Assignment

#### 1-Hour SO2

$$The number of quarterly summaries, with corresponding pollutant standard and exceptional data type, where the summary criterion is met. A quarter meets summary criterion when: • Annual Standard: Observation Percentage >= 75%. • 1-hour Standard: Percent Days >= 75%. Percent Days is the percentage of valid days (days where summary criterion is met, with respect to pollutant standard and exceptional data type) in a quarter compared to the total number of days in the quarter.$$

#### 1-Hour NO2

$$Number quarterly summaries, with the corresponding pollutant standard and exceptional data type, where the Percent Days >= 75%. Percent Days is the percentage of valid days (days with corresponding pollutant standard and exceptional data type, where summary criterion is met) in a quarter compared to the total number of days in the quarter.$$

#### All Others

This field is not calculated for other pollutant-duration combinations.

## Completeness Indicator

A flag indicating if the percent completeness is greater than or equal to 75.

## Completeness Percent

Annual Summary Percent completeness

## Compliance Date

The date on which the current status of the monitor's compliance with the regulation was achieved.

## Concurred Exclusions

If the operating agency has requested that data from this monitor be excluded from NAAQS calculations and the governing EPA regional office has agreed, the NAAQS standard(s) and the years of exclusion are listed.

## Concurred Null Observations

The number of sample data records in the aggregate calculation that are flagged with null data codes and for which there is regional concurrence.

## Confidence Limit Base

Defines the type of assessment the values is compared against to determine the number of values between the upper and lower confidence limits for the ASSESSMENT.

## Confidence Limit Equation

Defines the type of Confidence Limit (CL) calculation method required by the ASSESSMENT.

## Corrective Action Audit ID

The identifier of the Audit associated with the Corrective Action

## Corrective Action Date

The date of the Corrective Action.

## Count of PE's in Quarter 1-4

Number of Annual Performance Evaluation audit data records submitted for the indicated calendar quarter of the year.

## County

The name of the county where the monitoring site is located.

## County Code

The FIPS County Code where the monitor resides.

## Creditable Day Candidate Indicator

An indicator of whether this day is a candidate for a creditable sampling day.

## Creditable Day Indicator

An indication of whether the daily summary record is creditable, with S signifying a Scheduled Day and M a valid make-up day.

## Creditable Sample Count

Number of scheduled and make-up days that are given credit when determining data completeness for a site. (Note: This may not be the number of values averaged, since "extra samples" may be included in the mean.

### Value Assignment

#### PM2.5

The sum of valued, scheduled sampling days, plus make-ups for missing scheduled days.

Scheduled days are the number of days within the year that were scheduled for sampling, as determined by the EPA-defined calendar for the required collection frequency, and which also fall within the period of operation, as defined by sampling periods.

A make-up day is a sample recorded in the same stratum as, or exactly seven days after, a missing scheduled sample. In both conditions, the make-up sample must occur within the same quarter as the missed sample. A maximum of five make-up samples are allowed per quarter. (References: EPA-454/R-99-008 Guide line on Data Handling Conventions for the PM NAAQS; Memorandum: February 3, 1999 Use of Make-Up Samples to Replace Scheduled PM Samples.)

The sum of valued, scheduled sampling days, plus valid make-ups for missing scheduled days without respect to event exclusion.

Scheduled days are the days on which sampling is scheduled based on the required sampling frequency for the monitoring site. A scheduled day for a site is a day that is a scheduled day for any monitor at the site.

A valid Make-Up Sample:

• can be made by either the primary or collocated instruments;
• is either taken before the next required sampling day, or exactly one week after the missed (or voided) sampling day;
• may not be in another year than the missed sample;
• may be in another month than the missed sample;

Only two make-up samples are permitted each calendar month -- these are counted according to the month in which the miss and not the makeup occurred.

#### All Others

This field is not calculated for other pollutant-duration combinations.

## CSA

The name of the combined statistical area where the monitoring site is located.

## CSA Code

The code of the combined statistical area where the monitoring site is located.

## CSA Short Name

The short form of the OMB-assigned title for the combined statistical area (CSA).

## CV Estimate

Estimated coefficient of variance.

## Cylinder Certified Concentration

Gas concentration specified by cylinder producer.

## Cylinder ID

Unique identifier (e.g. serial number) of gas cylinder being assessed.

## Daily Arithmetic Mean

The measure of central tendency for the daily data set, obtained from the sum of the sample data or NAAQS averages divided by the number of values that comprise that sum.

## Daily Completeness Criteria Met

An indicator that all completeness criteria for the day were met so the calculated value is considered valid/creditable.

## Daily Maximum Hour

The hour of the day at which the DAILY_MAX_SAMPLE_VALUE was reported.

## Daily Maximum Value

The maximum sample data value or NAAQS average in the daily data set.

## Daily Observation Count

The number of values that comprise the daily data set

## Daily Observation Percent

The percentage of non-null sample data values or valid NAAQS averages in the daily data set compared to the maximum number of data values that could have been reported for the 24-hour period for the duration.

## Daily Rank

The rank of the Daily Maximum sample value relative the other maximum sample value for the same monitor in the same year.

## Daily Value

The combined daily value (whatever is appropriate for the parameter) for the site for the day. Thie is not calculated for every site-parameter combination in AQS.

## Data Capture Rate

Percentage of creditable samples vs scheduled samples (no rounding or truncation).

### Value Assignment

$$r = \frac {c}{s}$$

Where:
$$r =$$ data capture rate
$$c =$$ number of creditable samples
$$s =$$ number of scheduled samples

$$r = \frac {1}{n} {\sum_{i=1}^n C_i}$$

Where:
$$r =$$ data capture rate
$$n =$$ number of valid monthly summaries in the 3-month period
$$C_i =$$ the data capture rate for month i

## Data Status

Status Indicator is a code that indicates the processing status of a record. Only records with a status of P are in "Production" status and may be used for normal activities.

## Date

The date this data is relevant to.

## Datum

The Datum associated with the Latitude and Longitude measures.

## Design Value

The AQS calculated design value in the form of the indicated standard. It may be at the site level (for PM2.5 or Lead) or at the monitor level (all other parameters).

## Design Value for Annual Standard

The design value calculated using the procedures for the annual form of the standard: Average of DV year and 2 prior year's site-level weighted arithmetic mean.

## Design Value Using 24-hour Rules

The design value calculated using the procedures for the daily (24-hour) form of the standard: Average of current year and prior two calendar year Annual Summary 98th percentile values.

## Design Value Validity Indicator

Flag indicating whether the Design Value is valid (calculated using data that meets completeness criteria).

## Design Value Year

The year to which the calculated Design Value applies. This is generally the last year of a 3 year period. The years on the table are called "design value year", the previous year is "design value year - 1" and the first year of the period is "design value year - 2".

## Direction from Central Business District to Site

A representation of the true, as opposed to magnetic, direction of the site from the central business district. If the site is within the central business district, it is a representation of the direction the probe faces.

## Direction from Receiver to Transmitter

The direction from the receiver to the transmitter at the site.

## Direction from Site to Met Site

The true, as opposed to the magnetic, direction of the associated meteorological site from this site.

## Distance from Central Business District to Site

The distance, in kilometers, to the site from the center of the downtown central business district of the city in which the site is located.

## Distance from Monitor to Tangent Road

The distance in meters between the sensing of air sampling equipment at a monitoring site and the nearest edge of the roadway.

## Distance to Collocated Monitor

Distance from primary to QA collocated monitor.

## Distance to Meteorological Site

The distance of the associated meteorological site from the air quality monitoring site, in meters. This information is required if the site has monitors that are part of a Photochemical Assessment Monitoring System (PAMS) network. The associated site need not be an AQS site.

## Dominant Source Type

The primary source of the pollutant being monitored, e.g., point, area, mobile.

## Duplicate Value 1-5

A duplicate is when multiple samples are taken through the same sampler at the same time. There are 5 fields availble for reporting replicates. Report each replicate value starting in the first field, even if one has been reported as the raw data value.

## Eighth Max

8th highest value for year with the appropriate exceptional data type.

## Elevation

The elevation of the ground at the site in meters above mean sea level.

## Elevation Accuracy

The accuracy, in meters, of the elevation above mean sea level of a site.

## Elevation Collection Method

The method used to determine the Locational Data Policy (LDP) vertical measure. This data element is required by EPA LDP. More information regarding EPA’s data standards and policies may be found on EPA's Environmental Data Registry (EDR) Website (http://www.epa.gov/edr/).

## Elevation Collection Method Code

The method used to determine the Locational Data Policy (LDP) vertical measure. This data element is required by EPA LDP. More information regarding EPA’s data standards and policies may be found on EPA's Environmental Data Registry (EDR) Website (http://www.epa.gov/edr/).

## Elevation Datum

The Datum associated with the Elevation measure.

## EPA Region City

The name of the city where the EPA Regional Office with jurisdiction is located.

## EPA Region Code

An numerical identifier (with leading zero) for the EPA Region where the monitoring site resides.

## Error Code

The error code associated with a batch transaction error.

## Event Concurrence Indicator

Indicates whether the appropriate EPA regional office has concurred with either an event-qualified sample value, or a null ozone sample value qualified with the null data code “BG”, which signifies “Missing ozone data not likely to exceed level of standard”.

## Event Type

Indicates whether data measured during exceptional events are included in the summary. A wildfire is an example of an exceptional event; it is something that affects air quality, but the local agency has no control over. No Events means no events occurred. Events Included means events occurred and the data from them is included in the summary. Events Excluded means that events occurred but data form them is excluded from the summary. Concurred Events Excluded means that events occurred but only EPA concurred exclusions are removed from the summary. If an event occurred for the parameter in question, the data will have multiple records for each monitor.

## Exceedance Count

The number of times during the year the pollutant levels (expressed in the NAAQS average) exceeded the NAAQS standard.

## Exceptional Data Count

The number of data points in the annual data set affected by exceptional air quality events (things outside the norm that affect air quality).

## Exceptional Data Type Identifier

A designation indicating how a summary value is affected by exceptional events. It indicates whether exceptional data exists in the time period being summarized, and whether such exceptional data is included in the summary value.

For summaries of sample measurements, the following Exceptional Data Types are available:

0: No Events. None of the measurement data contributing to the summary has been flagged for exceptional events.

1: All Events Excluded. The summary excludes any measurements that have been flagged for exclusion because of exceptional events. (These measurements are excluded whether or not EPA has concurred with the flagging.)

2: All Events Included. Measurements included in the summary have been flagged for exceptional event exclusion but their data is included. (These measurements are included whether or not EPA has concurred with the flagging.)

5: Concurred Events Excluded. The summary excludes any measurements that have been flagged for exclusion for exceptional events AND the EPA Regional Office has concurred with the flagging.

For any site/monitor and summary time period, either a type 0 summary will exist (no data was flagged), or a type 1, type 2 and type 5 summary will all exist together.

For summaries created from lower-level summaries (e.g. daily summaries created from NAAQS_Average rows):

0: Created only when only lower-level summaries with EDT_ID = 0 exist

1: Created from lower-level summaries with EDT_ID 0 and 1

2: Created from lower-level summaries with EDT_ID 0 and 2

5: Created from lower-level summaries with EDT_ID 0 and 5

## Excluded Data Count

The number of reported data values flagged to be excluded from load processing.

## Exclusion Concurrence Comment

Free text commentary regarding the concurrence with the monitoring agency's request for exclusion from design value calculations for the specified standard.

## Exclusion Concurrence Date

The date/time on which the regional/headquarters user concurred with the monitoring agency's request for exclusion from design value calculations for the specified standard.

## Exclusion Concurrence Flag

Flag indicating NAAQS exclusion request status, may be NULL, 'Y' if accepted, or 'N' if rejected.

## Federal MDL

The minimum sample concentration detectable for the monitor and method as specified by EPA in the method description. Reporting agencies may specify and Alternate MDL which will override the Federal MDL.

## Fifth Max Date and Time

The date and time (on a 24-hour clock) when the fifth highest value for the year was taken.

## Fifth Max Value

The fifth highest value for the year.

## Filter Type

Type of filter loaded into this channel in sampler (e.g. Quartz)

## First Exceedance Date

Date of the first exceedance of the NAAQS standard during the year.

## First Max Date

The date when the highest value for the year was taken.

## First Max Date and Time

The date and time (on a 24-hour clock) when the highest value for the year was taken.

## First Max Hour

The time (on a 24-hour clock) when the highest value for the day was taken.

## First Max Value

The highest value for the year.

## First Non-Overlapping Max Date and Time

The date and time (on a 24-hour clock) when the first maximum non overlapping value for the year was taken.

## First Non-Overlapping Max Value

For 8-hour CO averages, the highest value of the year.

## Flow Rate Audit Bias Estimate

Flow Rate Audit bias estimate upper bound (90%)

## Flow Rate Audit Bias Sign

Flow Rate Audit bias sign

## Flow Rate Audit Percent Completeness

Flow Rate Audit percent completeness

## Flow Rate Type

The Type of flow associated with the monitor, when required. Values will be either HIGH or LOW.

## Flow Rate Verification Bias Estimate

Flow Rate Verification bias estimate

## Flow Rate Verification Bias Sign

Flow Rate Verification Bias Sign

## Flow Rate Verification Percent Completeness

Flow Rate Verification percent completeness

## Fourth Max Date

The date when the fourth highest value for the year was taken.

## Fourth Max Date and Time

The date and time (on a 24-hour clock) when the fourth highest value for the year was taken.

## Fourth Max Value

The fourth highest value for the year.

## Geometric Mean

The mean for the summarized sample set using a logarithm-based algorithm. (Only applicable to TSP and Lead.)

### Value Assignment

$$\mu = 10^x \quad \text{Where} \quad x = \frac {1} {n} \sum_{i=1}^n{\log_10 S_i}$$

Where:
$$\mu =$$ geometric mean
$$S =$$ sample value
$$n =$$ number of observations (during the year)

## Geometric Standard Deviation

The standard deviation of the logarithms of the sample values in the summarized sample set from the geometric mean. (Only applicable to TSP and Lead.)

### Value Assignment

$$\sigma = 10^x \quad \text{Where} \quad x = \sqrt{\frac { \left ( n \cdot \sum_{i=1}^n{\log_10 S_i^2} \right) - \left( \sum_{i=1}^n{\log_10 S_i} \right)^2 } {n \cdot (n-1)}}$$

Where:
$$\sigma =$$ geometric stamdard deviation
$$S =$$ sample value
$$n =$$ number of observations (during the year)
If the count of observations is 1, or the square root operand above is negative, the geometric standard deviation is assigned a value of zero.

## GMT Offset

The number of hours between Greenwich Mean Time and Local Standard Time at the monitor.

## Hi Vol Indicator

An indicator that the method used has a high volume flow rate.

## Indicated Value

For quality assurance calculations, the measurement recorded by a monitor for a standard gaseous concentration or flow with which it has been challenged. For QA collocated monitors, the sample value from the "duplicate" sampler. This value may also be reported as the Sample Value on the raw data transaction and the Known Mass should not be substituted for the Sample Value when using data extracted from AQS.

## Known Mass

For a quality assurance assessment, the known mass of analyte on the test media. This is also called the "assessment mass".

## Laboratory Response Value

For Lead analysis audit quality assurance assessments, the mass of lead reported by lab. This is not a Lead sample value.

## Land Use Type

A category describing the predominant land use within a 1/4 mile radius of the site. Valid values are: Agricultural, Blighted Areas, Commercial, Desert, Forest, Industrial, Military Reservation, Mobile, Residential.

## Last Change Date

This represents the date the most relevant underlying data in AQS was last changed. That is, for annual summary data, it is the date these values were last affected by a change in raw data. If the AQCR code on the annual summary view changed, the date of last change would not be updated.

## Last Method Begin Date

Many tables show the method currently used by a monitor. This field shows the date on which that method began being used for the monitor.

## Last Method Used

Many tables show the method currently used by a monitor. This field shows the description of that method. The description is a concatenation of the sample Method of Collection and Method of Analysis.

## Last Method Used Code

Many tables show the method currently used by a monitor. This field shows the AQS method code for that method.

## Last Post Date

The last date on which raw data was added to this monitor (this is not the sample date, but the date on which processing happened).

## Last Sample Date

The last date on which AQS has raw data that was collected from this monitor.

## Last TSA Date

Date of last Technical Systems Audit for a PQAO-Parameter combination.

## Lat Lon Accuracy

The accuracy of the latitude and longitude coordinates in meters.

## Lat Lon Collection Method

Method used to determine the latitude/longitude or UTM coordinates. Required by EPA Locational Data Policy (LDP). More information regarding EPA’s data standards and policies may be found on EPA's Environmental Data Registry (EDR) Website (http://www.epa.gov/edr/).

## Lat Lon Collection Method Code

Method used to determine the latitude/longitude or UTM coordinates. Required by EPA Locational Data Policy (LDP). More information regarding EPA’s data standards and policies may be found on EPA's Environmental Data Registry (EDR) Website (http://www.epa.gov/edr/).

## Latitude

The angular distance north or south of the equator measured in decimal degrees. North is positive.

## Lead Analysis Level 1 Known Mass

The known mass of lead on the analyzed strip or filter for the legacy monitor-level lead analysis audit at level 2.

## Lead Analysis Level 1 Lab Response

The value measured by the lab for the legacy monitor-level lead analysis audit at level 1.

## Lead Analysis Level 2 Known Mass

The known mass of lead on the analyzed strip or filter for the legacy monitor-level lead analysis audit at level 1.

## Lead Analysis Level 2 Lab Response

The value measured by the lab for the legacy monitor-level lead analysis audit at level 2.

Flag indicating whether the summary is valid. Set to 'Y' if there are 12 valid months or the maximum 3-month rolling average exceeds the standard; otherwise 'N'

Status of PQAO-Level Lead Analysis Summary

## Legacy Audit Number

The audit ID provided by the user on the legacy transaction. It may differ from ASSESSMENT_NUM, which is generated.

## Level 1 Assessment Concentration

The value of the known gas standard concentration in Audit Level 1.

## Level 1 Count

Number of Level 1 values submitted.

## Level 1 Monitor Concentration

The concentration value provided by the monitor being assessed at level 1.

## Level 10 Assessment Concentration

The value of the known gas standard concentration in Audit Level 10.

## Level 10 Count

Number of Level 10 values submitted.

## Level 10 Monitor Concentration

The concentration value provided by the monitor being assessed at level 10.

## Level 2 Assessment Concentration

The value of the known gas standard concentration in Audit Level 2.

## Level 2 Count

Number of Level 2 values submitted.

## Level 2 Monitor Concentration

The concentration value provided by the monitor being assessed at level 2.

## Level 3 Assessment Concentration

The value of the known gas standard concentration in Audit Level 3.

## Level 3 Count

Number of Level 3 values submitted.

## Level 3 Monitor Concentration

The concentration value provided by the monitor being assessed at level 3.

## Level 4 Assessment Concentration

The value of the known gas standard concentration in Audit Level 4.

## Level 4 Count

Number of Level 4 values submitted.

## Level 4 Monitor Concentration

The concentration value provided by the monitor being assessed at level 4.

## Level 5 Assessment Concentration

The value of the known gas standard concentration in Audit Level 5.

## Level 5 Count

Number of Level 5 values submitted.

## Level 5 Monitor Concentration

The concentration value provided by the monitor being assessed at level 5.

## Level 6 Assessment Concentration

The value of the known gas standard concentration in Audit Level 6.

## Level 6 Count

Number of Level 6 values submitted.

## Level 6 Monitor Concentration

The concentration value provided by the monitor being assessed at level 6.

## Level 7 Assessment Concentration

The value of the known gas standard concentration in Audit Level 7.

## Level 7 Count

Number of Level 7 values submitted.

## Level 7 Monitor Concentration

The concentration value provided by the monitor being assessed at level 7.

## Level 8 Assessment Concentration

The value of the known gas standard concentration in Audit Level 8.

## Level 8 Count

Number of Level 8 values submitted.

## Level 8 Monitor Concentration

The concentration value provided by the monitor being assessed at level 8.

## Level 9 Assessment Concentration

The value of the known gas standard concentration in Audit Level 9.

## Level 9 Count

Number of Level 9 values submitted.

## Level 9 Monitor Concentration

The concentration value provided by the monitor being assessed at level 9.

## Local Primary Standard

A description of the source of the local primary standards.

## Local Region Code

A code representing a state-defined geographic/administrative area within which the site is located.

## Local Region Name

The name of a state-defined geographic/administrative area within which the site is located.

## Local Site Name

The identifier of the site in the onwning agency's (e.g., not US EPA) nomenclature.

## Local Site Number

An identifier for the site in the onwning agency's (e.g., not US EPA) numbering scheme.

## Local Standard Expiration Date

The expiration date for any local primary air quality standard that may be defined.

## Location Setting

A description of the setting within which the monitoring site is located, e.g., rural, urban, or suburban.

## Longitude

The angular distance east or west of the prime meridian measured in decimal degrees. East is positive, West is negative.

## Lower Confidence Limit

The lower probability limit (95% confidence) of the compared percent differences. This is calculated for quality assurance assessment results.

### Value Assignment

#### PM2.5 Flow

$$l = D - \left( \frac {1}{\sqrt{n}} \cdot {S \cdot t_{0.975, n-1}} \right)$$

Where:
$$l =$$ lower 95% confidence limit
$$D =$$ mean value
$$S =$$ standard deviation
$$t_{0.975, n-1} =$$ the 0.975 quantile of the Student's T distribution with n-1 degrees of freedom
$$n =$$ number of values or audits

#### PM2.5 Collocated Mass

$$l = CV \cdot \sqrt{ \frac {n} {\chi_{0.95, n}^2} }$$

Where:
$$l =$$ lower 90% confidence limit
$$CV =$$ coefficient of variation
$$S =$$ standard deviation (from reporting organization accuracy summary)
$${\chi_{0.95, n}^2} =$$ the 0.975 quantile of the Student's T distribution with n-1 degrees of freedom
$$n =$$ number of values or audits

#### Other Collocated

$$l = D - \left( \frac {1}{\sqrt{2}} \cdot {S \cdot 1.96} \right)$$

Where:
$$l =$$ lower 95% confidence limit
$$D =$$ mean value
$$S =$$ standard deviation

#### FRM Audit

$$l = D - \left( \frac {1}{\sqrt{n}} \cdot {S \cdot t_{0.975, n-1}} \right)$$

Where:
$$l =$$ lower 95% confidence limit
$$D =$$ mean value
$$S =$$ standard deviation
$$t_{0.975, n-1} =$$ the 0.975 quantile of the Student's T distribution with n-1 degrees of freedom
$$n =$$ number of values or audits

#### All Others

$$l = D - \left( S \cdot 1.96 \right)$$

Where:
$$l =$$ lower 95% confidence limit
$$D =$$ mean value
$$S =$$ standard deviation

## Lower Limit

The lower bound of the value range

## Maximum 3-Month Rolling Average

The maximum arithmetic mean for the 3-month rolling periods, (e.g., January-March, February-April), in the summarized year. This is calculated as an intermediate step for Lead desing vlaues.

## Measurement Scale

A denotation of the geographic scope of the air quality measurements made by the monitor. The implication is that the same measurement made elsewhere within the measurement scale would produce an equivalent result to that produced at the monitoring site.

## Measurement Scale Definition

A numeric distance that reflects the Measurement Scale geographic scope.

## Measurement Uncertainty

The total measurement uncertainty associated with a reported measurement as indicated by the reporting agency. This includes method uncertainty, both the analytical and the volume uncertainty. No blank corrections are assumed (other than laboratory baseline corrections which are an integral part of each analysis).

## Met Site ID

The AQS site ID where meteorological data is collected, if not collected at this site.

## Met Site Type

The type of meteorological station that has been paired with this site for meteorological data. Sites with monitors in a Photochemical Assessment Monitoring System (PAMS) network must have a paired meteorological site identified. (Just because a site does not list "on site met equipment" does NOT mean it does not have on site met instruments.)

## Method

A short description of the processes, equipment, and protocols used in gathering and measuring the sample. This field is a concatenation of the method of collection and the method of analysis.

## Method Code

A three digit code representing the measurement method. A method code is only unique within a parameter (that is, method 111 for ozone is not the same as method 111 for benzene).

## Method Count

The number of methods used to collect samples for the monitor during the aggregation period (e.g., year).

## Method Detection Limit (MDL)

The minimum sample concentration detectable for the monitor and method. Each method has a federal MDL assigned to it by the EPA. If the analyzing agency has determined and reported their own MDL, this will be listed rather than the federal MDL.

## Method of Analysis

A description of the method used to determine the parameter measurement after the atmospheric sample has been collected. This may be an in-situ meeasurement (taken automatically at the site) or a laboratory method which is used after the sample has been transferred to the analyzing laboratory.

## Method of Collection

A description of the method used by the monitor to collect an atmospheric sample. In some cases this is a sampler model number or description. In others it is a conceptual description.

## Method Type

An indication of whether the method used to collect the data is a federal reference method (FRM), equivalent to a federal reference method, an approved regional method, or none of the above (non-federal reference method).

## Minimum Value

The lowest sample value recorded during the aggregation period.

## Missing Days Assumed Below Standard

The number of invalid or missing days in the effective monitoring season whose daily maxima are assumed to be less than or equal to the standard. (Only applicable to 1-hour and 8-hour ozone.)

### Value Assignment

#### 1-Hour Ozone

A missing or invalid day is assumed to be less than the standard when either of the following conditions exists:
• The daily maximums on the days immediately preceding, and immediately succeeding, the missing day were less than, or equal to, 75% of the standard.
• The nu\mber of valid samples for the day was less than 18, and the sum of the following is greater than, or equal, to 18, i.e., 75% of the possible values:
• Number of valid samples;
• Number of null samples that were both flagged as not likely to exceed the standard, and for which the Regional Office has indicated concurrence;
• Number of omitted samples that were flagged with event qualifiers, and for which the Regional Office has indicated concurrence.

#### 8-Hour Ozone

A missing or invalid day is assumed to be less than the standard for the following condition: The number of valid 8-hour arithmetic averages for the day was less than 18, and the sum of the following is greater than, or equal, to 18, i.e., 75% of the possible values:
• Number of valid 8-hour arithmetic averages;
• Number of missing 8-hour arithmetic averages that would be valid if excluded samples (null or event-qualified) were included, where those excluded samples have concurrence from the EPA Regional Office.

#### All Others

This field is not calculated for other parameter-duration combinations.

## Molecular Weight

The sum of the atomic weights of a molecule's constituent atoms.

## Monitor Channel Begin Date

Beginning of date range where the monitor was operating on the sampler channel

## Monitor Channel End Date

End of date range where the monitor was operating on the sampler channel

## Monitor Close Date

The date on which the operating agency indicated that the monitor ceased operating. (If there is no value, then the monitor is open.)

## Monitor Compliance Indicator

The compliance status of a monitor with respect to an EPA regulation.

## Monitor Concentration

For quality assurance assessments, the concentration value provided by the monitor being assessed. For normal sampling the value is reported as the Sample Value (on the Raw Data transaction).

## Monitor Count

The number of monitors in the group identified by the previous fields in the report.

## Monitor Flow Rate

The measured flow rate provided by the monitor being assessed.

## Monitor ID

The AQS Monitor ID in the format XX-YYY-ZZZZ-PPPPP-A where:

• XX is the State FIPS code or Tribal Site identifier ("TT"),
• YYY is the County FIPS code or Tribal Code,
• ZZZZ is the site number within the county or tribal land,
• PPPP is the parameter code, and
• A is the POC.

## Monitor Method Code

A three digit code representing the measurement method of the operational monitor. A method code is only unique within a parameter (that is, method 111 for ozone is not the same as method 111 for benzene).

## Monitor Objective

Identification of the reason for measuring air quality by the monitor.

## Monitor Project Type

A code that identifies the type of sampling (population-oriented, source-oriented, background, etc.) performed by the monitor.

## Monitor Recording Mode

Generic description of the type of sampling the instrument is performing (CONTINUOUS or INTERMITTENT).

## Monitor Screening Group

The number of the Screening Group to which the monitor belongs.

## Monitor Status

The AQS processing status of the monitor record. P means the data is at production status and is suitable for use. Any other status indicates that data is missing or does not pass screening tests and the data should not be used.

## Monitor Type

An administrative or regulatory classification for the monitor.

## Monitor Type Abbreviation

An administrative or regulatory classification for the monitor.

## Monitor Type Begin Date

The beginning of the time period during which the monitor was assigned the monitor type.

## Monitor Type End Date

The end of the time period during which the monitor was assigned the monitor type.

## Monitoring Agency

The name of the agency responsible for operating the monitor.

## NAAQS Date and Time

The date and time, in local standard time, to which the NAAQS average calculation applies.

## NAAQS Description

Long description of the National Ambient Air Quality Standard.

## NAAQS Statistic

Descriptive name for statistic used for comparison with NAAQS standard level (e.g. Annual 4th Maximum).

## Negative Percent Difference Count

The number of calculated percent differences that were negative (below zero).

## Network

A list of the monitoring networks (groups of monitors with common goals and procedures) to which the monitor belongs.

## Network Code

An abbreviated form of the Network.

## NPAP Analysis Method

A description of the analysis method used by the assessment monitor to determine the measurement.

## NPAP Audit Valid Indicator

Indicates whether there are at least 3 valid levels, 1 = TRUE, 0 = FALSE.

## NPAP Bias

National Performance Audit Program Bias Estimate.

## NPAP Collection Method

A description of the sample collection method used by the assessment monitor to determine the measurement.

## NPAP Method Code

A three digit code representing the measurement method of the assessment monitor. A method code is only unique within a parameter (that is, method 111 for ozone is not the same as method 111 for benzene).

## NPAP PQAO Status

Status (Y/N) of NPAP PQAO-Level Summary

## NPAP Type

The type of NPAP audit: TTP for "Through the probe" or BOA for "Back of analyzer".

## NPAP Valid Assessment Count

Number of Monitor Level NPAP Assessments submitted where at least 3 levels meet bias criteria

## Null Data Reason

A reason explaining why no sample or blank value was reported for the scheduled sampling time.

## Null Data Reason Code

A code explaining why no sample or blank value was reported.

## Null Observation Count

When a monitor does not make a scheduled sample, it should report a "null data reason code". This is the count of null data codes reported during the summary period.

## Observation Count

The number of observations (samples) taken during the averaging period.

## Observation Percent (Annual)

The percent of recorded sample values that were reported compared to the number of data values that were scheduled to have been reported for the year.

### Value Assignment

#### 1-Hour Ozone

$$p = \frac {v} {r} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of valid days
$$n =$$ number of required days

#### 8-Hour Ozone

$$p = \frac {(v+a)} {r} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of valid days
$$a =$$ number of missing days assumed less than standard
$$n =$$ number of required days

#### Daily PM2.5 and PM10

$$p = \frac {v} {n} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of valid days
$$n =$$ number of required (e.g., scheduled) days

#### 1-Hour SO2

$$p = \frac {s} {m} \cdot 100$$

Where:
$$p =$$ observation percent
$$s =$$ number of sample observations
$$m =$$ number hours in the year (maximum possible number of sample observations)

#### 1-Hour NO2

$$p = \frac {s} {m} \cdot 100$$

Where:
$$p =$$ observation percent
$$s =$$ number of sample observations
$$m =$$ number hours in the year (maximum possible number of sample observations)

#### Other Hourly

$$p = \frac {n} { a \cdot \left( \frac {24} {l} \right) } \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of valid days
$$a =$$ number of active days in the year
$$l =$$ length of each sample (sample duration) in hours

## Observation Percent (Daily)

The percent of sample values that were reported compared to the number of data values scheduled to have been reported for the 24-hour (midnight to midnight local time) period.

### Value Assignment

$$p = \frac {n} { \left( \frac {24} {l} \right) } \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of valid days
$$l =$$ length of each sample (sample duration) in hours

## Observation Percent (Quarterly)

The percent of sample values that were reported compared to the number of data values scheduled to have been reported for the quarter.

### Value Assignment

#### 1-Hour and 8-Hour Ozone

$$p = \frac {n} { \left( q \cdot 24 \right) } \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of samples
$$q =$$ number of active days in the quarter

#### 24-Hour PM2.5 and PM10

$$p = \frac {n} {q} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of samples
$$q =$$ number of active days in the quarter

#### Daily PM10

$$p = \frac {v} {q} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of samples
$$q =$$ number of active days in the quarter

#### Daily PM2.5

$$p = \frac {v} {r} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of valid days
$$r =$$ number of required (schedule) days

#### Site Level PM2.5

$$p = \frac {v} {r} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of valid days
$$r =$$ number of required (schedule) days

#### 1-Hour SO2

$$p = \frac {n} {m} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of sample observations
$$m =$$ maximum number of observations possible (e.g., hours in the quarter)

#### 1-Hour NO2

$$p = \frac {n} {m} \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of sample observations
$$m =$$ maximum number of observations possible (e.g., hours in the quarter)

#### Other Hourly

$$p = \frac {n} { a \cdot \left( \frac {24} {l} \right) } \cdot 100$$

Where:
$$p =$$ observation percent
$$v =$$ number of samples
$$a =$$ number of active days in the quarter
$$l =$$ length of each sample (sample duration) in hours

## Observations Below the MDL

The count of sample observations that were below the method detection limit (MDL) *and* had their sample value replaced with 1/2 of the MDL by AQS. Note, AQS is in the process of removing 1/2 MDL substitution for all paramters and this is expected to be complete in early 2016.

## Observations with Events

The number of observations in the aggregation period that were flagged as being affected by an event.

## Open Path Beam Length

The length of the beam projected between the transmitter and the receiver at the site, in meters.

## Open Path Maximum Beam Height

For an open path monitor, the height of the beam (at the highest point from the ground) being projected between the receiver and transmitter at the site, in meters.

## Open Path Minimum Beam Height

For an open path monitor, the height of the beam (at the lowest point from the ground) being projected between the receiver and transmitter at the site, in meters.

## Open Path Number

For an open path monitor, the unique numeric identifier for the open path at the site.

## Open Path Transmitter Height

The height of the open path transmitter above the ground, in meters.

## Owning Agency

The name of the agency assigned as the owner of the site.

## Owning Agency Code

The code of the agency assigned as the owner of the site.

## Ozone SRP Verification Type

The type of standard reference photometer verification being performed. "6X6" is for the initial verification of a new standard ozone generator. "Standard" is for a routine SRP assessment.

## Parameter

The name or description assigned in AQS to the parameter measured by the monitor. Parameters may be pollutants or non-pollutants (e.g., wind speed).

## Parameter Class

The class of parameters to which this one belongs (e.g., Criteria, HAPS, Speciation). A parameter may belong to many classes.

A parameter class is a grouping of parameters. They may be grouped because of chemical similarities, regulatory definitions, or convenience of reporting.

## Parameter Class Code

The short name of the classification to which the parameter belongs.

## Parameter Code

The AQS code corresponding to the parameter measured by the monitor.

## Parameter Code Assessed at Lab

This is the parameter code the assessment was made against (the monitor parameter code is listed separately in case there is a difference).

## Parameter Code of the Monitor Being Assessed

This is the parameter code the monitor being assessed (the assessment parameter code is listed separately in case there is a difference).

## Parameter Type

A type used in the evaluation of precision and accuracy input transactions for assignment to QA value types, e.g., gaseous, PM2.5, other PM.

## PE Bias Estimate Upper Bound

Annual Performance Evaluation Bias upper bound

## PE Completeness Percent

Annual Performance Evaluation Completeness percent

## PE Level

The level of the Performance Evaluation audit being performed. The range values for these levels are defined in 40 CFR Part 58 Appendix A.

## PEP Assessments Observed

The number of PEP (performance evaluation program) assessment observations that were reported to AQS.

## PEP Assessments Required

The number of PEP (performance evaluation program) assessment observations that are required to meet regulatory obligations.

## PEP Audits Percent

The percentage of required Collocated Performance Evaluation Program (PEP) audits performed. This value is only computed for SUMMARY rows, where applicable.

## PEP Collocated Audits

The number of Collocated Performance Evaluation Program (PEP) audits collected. This value is only computed for SUMMARY rows, where applicable.

## PEP Collocated Indicator

An indicator if the sample is a collocated Performance Evaluation Program sample.

## PEP Collocated Observations

Lead Only: Number of Collocated PEP Audits Collected

## PEP Collocated Required

The number of Collocated Performance Evaluation Program (PEP) audits required to be collected. This value is only computed for SUMMARY rows, where applicable.

## PEP Concentration

The value reported by the PEP monitor for the Date-Time.

## PEP Method Code

A three digit code representing the measurement method of the assessment monitor. A method code is only unique within a parameter (that is, method 111 for ozone is not the same as method 111 for benzene).

## PEP Method of Analysis

A description of the analysis method used by the assessment monitor to determine the measurement.

## PEP Method of Collection

A description of the sample collection method used by the assessment monitor to determine the measurement.

## PEP Methods Audited

Number of distinct methods audited via PEP assessments.

## PEP PQAO Status

Status of PQAO-Level PEP Summary

## PEP Type

Indicates where the PEP monitor is operated by the Audit Agency or by the Monitoring Agency.

## Percent Complete

The percentage of required observations (or scheduled days) made for the given assessment time period.

## Percent Difference

The relative difference between the known and measured concentrations, expressed as a percentage.

### Value Assignment

$$d = \frac { \left( X - Y \right) } {Y} \cdot 100$$

Where:
$$d =$$ percent difference
$$X =$$ indicated (measured) concentration or flow rate
$$Y =$$ known (true) concentration or flow rate

## Percent Difference Count

The total number of percent difference calculations that were able to be performed across all levels of the assessment.

## Percent Difference Equation

Defines the type of PERCENT DIFFERENCE calculation method required by the ASSESSMENT.

## Percent Difference for SRP Assessment 1-10

The relative difference between the known and measured concentrations for the given assessment, expressed as a percentage.

## Percent of Days with One Sample

Percentage of days with at least one sample measurement (ignoring flagging and concurrence).

### Value Assignment

#### 1-Hour SO2

$$p = \frac {s} {d}$$

Where:
$$p =$$ percent of days
$$s =$$ valid day count
$$d =$$ number of required (scheduled) days

#### 1-Hour NO2

$$p = \frac {s} {d}$$

Where:
$$p =$$ percent of days
$$s =$$ valid day count
$$d =$$ number of required (scheduled) days

#### All Others

$$p = \frac {s} {d}$$

Where:
$$p =$$ percent of days
$$s =$$ valid day count
$$d =$$ number of required (scheduled) days

## Performing Agency

The name of the Agency or organization performing the quality assurance assessment.

## Performing Agency Code

A code representing the Agency or organization performing the quality assurance assessment.

## PM 10 Assessment Flow Rate

For PM10 flow rate quality assurance checks, the flow rate of the flow transfer standard.

## PM 10 Method

The sampling methodology name of the PM10 monitor being assessed.

## PM 10 Method Code

The sampling methodology code of the PM10 monitor being assessed.

## PM 10 Method of Analysis

Description of analysis method for PM10 samples.

## PM 10 Method of Collection

Description of collection method for PM10 samples.

## PM 10 Monitor Flow Rate

For PM10 flow rate quality assurance checks, the measured flow rate provided by the monitor being assessed.

## PM 10 Percent Difference

For PM10 flow rate quality assurance checks, the relative percent difference of the monitor and assessment flow rates.

## PM 2.5 Assessment Flow Rate

For PM2.5 flow rate quality assurance checks, the flow rate of the flow transfer standard.

## PM 2.5 Method

The sampling methodology name of the PM2.5 monitor being assessed.

## PM 2.5 Method Code

The sampling methodology code of the PM2.5 monitor being assessed.

## PM 2.5 Method of Analysis

Description of analysis method for PM2.5 samples.

## PM 2.5 Method of Collection

Description of collection method for PM2.5 samples

## PM 2.5 Monitor Flow Rate

For PM2.5 flow rate quality assurance checks, the measured flow rate provided by the monitor being assessed.

## PM 2.5 Percent Difference

For PM2.5 flow rate quality assurance checks, the relative percent difference between the monitor and assessment flow rates.

## POC

This is the "Parameter Occurrence Code" used to distinguish different instruments that measure the same parameter at the same site. There is no meaning to the POC (e.g. POC 1 does not indicate the primary monitor). For example, the first monitor established to measure carbon monoxide (CO) at a site could have a POC of 1. If an additional monitor were established at the same site to measure CO, that monitor could have a POC of 2. However, if a new instrument were installed to replace the original instrument used as the first monitor, that would be the same monitor and it would still have a POC of 1.

## Pollutant Area

Designation of a pollutant area to which the monitor is assigned. Pollutant areas are geographic areas defined by a program office in which a certain pollutant should be closely watched. Most are problem or non-attainment areas, but attainment areas requiring special attention may also be defined. Types of pollutant areas are: status areas, monitoring areas, and monitor planning areas.

## Pollutant Area Code

Designation of a pollutant area to which the monitor is assigned. Pollutant areas are geographic areas defined by a program office in which a certain pollutant should be closely watched. Most are problem or non-attainment areas, but attainment areas requiring special attention may also be defined. Types of pollutant areas are: status areas, monitoring areas, and monitor planning areas.

## Pollutant Area Type

The type of pollutant area, such as status area, monitoring area, monitor-planning area.

## Pollutant Standard

A description of the ambient air quality standard rules used to aggregate statistics. A pollutant standard will include the year of promulgation and the form of the standard.

## Pollutant Standard Summary Metric Used

The base metric used in the calculation of the aggregate statistics presented in the remainder of the row. This corresponds to a form of a pollutant standard. For example, if this is Daily Maximum, then the value in the Mean column is the mean of the daily maximums.

## PQAO

The name of the agency assigned as Primary Quality Assurance Organization for the monitor reporting data.

## PQAO Begin Date

The date on which the indicated agency became the Primary Quality Assurance Organization for the monitor.

## PQAO Code

The code representing the Primary Quality Assurance Organization for this monitor.

## PQAO End Date

The date on which the indicated agency ceased being the Primary Quality Assurance Organization for the monitor.

## Primary Exceedance Count

The number of samples during the year that exceeded the primary air quality standard.

## Primary Monitor for NAAQS Indicator

An indication of whether this is the primary monitor for the pollutant at the site for standards compliance when more than one monitor is operating at the site.

## Primary Monitor for QA Indicator

An indication of whether this is the primary monitor for the pollutant at the site when collocated monitors are used for quality assurance purposes.

## Primary Monitor POC

The POC of the NAAQS primary monitor on the indicated date as assigned on the site "primary monitor periods" record.

## Primary Standard Level

The level (concentration value) of the primary national ambient air quality standard for the pollutant.

## Probe Height

The height of the sampling monitor probe from the ground, in meters.

## Probe Horizontal Distance

The horizontal distance of the monitor's probe from the probe's support structure, in meters.

## Probe Location

A general location of the monitor's probe with respect to the building where the monitor itself is located, e.g., "top of building", "ground level"

## Probe Obstruction Distance

The vertical distance of the monitor's probe from the obstruction, in meters.

## Probe Obstruction Height

The height, in meters, of the top of the obstruction above the level of the probe.

## Probe Obstruction Type

The type of obstruction responsible for the restricted airflow of a monitor.

## Probe Vertical Distance

The vertical distance of the monitor's probe from the probe's support structure, in meters.

## Processing Error

The Error AQS encountered when attempting to load the data.

## Processing Failed Transaction Count

The number of transactions that failed to load into the database.

## Processing Final Status

Final status message from load process.

## Processing Status

Processing state for the submission. (Can also be the QAPP approval status.) P means the data is posted to production and public.

## Producer ID

Unique identifier of organization that produced cylinder being assessed.

## Producer Name

Description of organization that produced cylinder being assessed.

## Promulgation Date

The date the standard was promulgated (finalized in the federal register).

## QAPP Approval Date

Date the Quality Assurance Project Plan was approved.

## QAPP Approval Indicator

Status (Y/N) of QAPP meeting certification criteria

## QAPP Evaluation Comment

Comment provided by approving official.

## QAPP Evaluation Date

Date that evaluating official decides upon document status

## QAPP Submission Date

Date when the quality management plan is received by the approving organization.

## QMP Approval Date

Date when the quality management plan is approved by the approving organization

## QMP Approving Agency

Agency Code of the organization approving the quality management plan

## QMP Approving Agency Code

The name of the organization approving the quality management plan

## Qualifier 1-10

The code for the qualifier affecting the sample or blank measurement. Up to 10 qualifier may be entered for each measurement. A qualifier is any note about the data from the AQS qualifiers list that applies to the reported measurement.

## Quality Assurance Agency

The name of the prevailing QA agency of a selected site and parameter during a reported year for the Combined Site Sample Value Listing request.

## Quality Assurance Agency Code

The code of the prevailing QA agency of a selected site and parameter during a reported year for the Combined Site Sample Value Listing request.

## Quality Assurance Assessment Name

The type of assessment being performed (1-point check, collocation, etc.).

## Quarter Number

Number (1-4) of the calendar quarter in the year to which the data applies. For example, the quarter in which the first exceedance occurred.

## Quarterly Completeness Criteria Met

An indicator that the quarterly data completeness criteria were met by the monitor.

## RCF Begin Date

The beginning of the date range to which the Required Collection Frequency schedule applies.

## RCF Code

The Required Collection Frequency (how often a sample must be collected) of the monitor. Mandatory for Photochemical Assessment Monitoring System (PAMS) organic compound, PM2.5, and PM10 monitors.

## RCF End Date

The end of the date range to which the Required Collection Frequency schedule applies.

## Regulation Code

A code that represents an EPA regulation for which compliance documentation is required.

## Regulation Compliance Date

The date on which the monitor was deemed to be in compliance with the listed regulation.

## Regulation Compliance Status

An indicator that the monitor is in compliance with the listed regulation.

## Regulatory Monitor Indicator

Indicator (“Yes”, “No”) as to whether or not the monitor being assessed is marked as “Regulatory”

## Replicate Value 1-5

A replicate is when a single atmospheric sample is analyzed multiple times to determine the precision of the measuement instrument. There are 5 fields available to report replicate analyses (measurements) of the sample. Report each replicate value starting in the first field. Report all replicate values in the record (even if one of the values is reported as raw data).

## Reported Unit

The units of measure in which the sample value was reported.

## Reported Unit Code

A code indicating units of measure in which the sample value was reported.

## Reporting Agency

The name of the agency assigned as "Reporting" data for the monitor reporting data.

## Reporting Agency Code

The code of the agency assigned as "Reporting" data for the monitor reporting data.

## Required Day Count

The number of days during the year which the monitor was scheduled to take samples if measurements are required.

### Value Assignment

#### 1-Hour and 8-Hour Ozone

The number of active days within the effective monitoring season.

#### Daily PM10 and PM2.5

Scheduled days are the number of days within the year that were scheduled for sampling, as determined by the EPA-defined calendar for the required collection frequency, and which also fall within the period of operation, as defined by sampling periods.

Seasonal and random frequencies are sub-divided in monthly-required frequencies; otherwise, the required frequency applies to a defined period of time. A PM10 or PM2.5 monitor must have a defined collection frequency for each active day, by rule.

The reference point for the EPA calendar is January 4, 1956. For example, in the year 2003, the every 6th day calendar would comprise: 1/3/2003, 1/9/2003, 1/15/2003, etc., and the every 3rd day calendar would comprise: 1/3/2003, 1/6/2003, 1/9/2003, 1/12/2003, etc. For a monitor doing seasonal sampling, with every 6th day sampling in April and every 3rd day sampling in May, both months in 2003, the schedule would be as follows: 4/15/03, 4/21/03, 4/27/03, 5/3/03, 5/6/03, 5/9/03, etc.

#### 24-Hour PM2.5 and PM10

The number of active days in the year.

#### All Others

This field is not calculated for other pollutant-duration combinations.

The name of a street adjacent or near the monitoring site.

A sequential number assigned to each road near a site.

The type of road or street being described.

## Sample Begin Date and Time

The date and time at which the sample began being taken. This value plus the sample duration indicates the end time of the sample.

## Sample Count

The total number of reported samples for the monitor-duration during the time range.

## Sample Date in Local Time

The date the sample was taken in Local Standard Time. This time reflects the beginning of the sample duration. That is, if the time is 2:00 and the duration is 1-hour, then sampling happened from 2:00 - 3:00.

## Sample Duration

The length of time that air passes through the monitoring device before it is analyzed (measured). So, it represents an averaging period in the atmosphere (for example, a 24-hour sample duration draws ambient air over a collection filter for 24 straight hours). For continuous monitors, it can represent an averaging time of many samples (for example, a 1-hour value may be the average of four one-minute samples collected during each quarter of the hour).

## Sample Duration Code

A code representing the Sample Duration. The code does not necessarily correspond to a real world value (e.g., "5" is not for a 5 hour sample duration).

## Sample Frequency

The frequency at which sample observations are made. Specified as the amount of time that elapses between the beginning of subsequent observations. Usually, this indicates how often 24-hour samples are taken, e.g., daily, every third day, stratified random, etc. This value is null for continuous (hourly) samplers

## Sample Frequency Code

The frequency at which sample observations are made. Specified as the amount of time that elapses between the beginning of subsequent observations. Usually, this indicates how often 24-hour samples are taken, e.g., daily, every third day, stratified random, etc. This value is null for continuous (hourly) samplers

## Sample Measurement

The measured value in the standard units of measure for the parameter.

## Sample Method of Analysis

The method by which the sample is analyzed to determine a pollutant value.

## Sample Method of Collection

The method by which the sample is collected from the atmosphere.

## Sample Residence Time

The time in seconds for the sample to move from the probe inlet to the monitor.

## Sampler Begin Date

Beginning of date range where the sampler is in use at the site

## Sampler Channel Begin Date

Beginning of date range where the channel has the specified metadata

## Sampler Channel Count

Number of distinct concurrent samples that can be taken by the sampler

## Sampler Channel End Date

End of date range where the channel has the specified metadata

## Sampler Channel Number

Number assigned to the channel on the sampler definition.

## Sampler Channel Target Flow Rate

Nominal flow rate for channel

## Sampler End Date

End of date range where the sampler is in use at the site

## Sampler Flow Rate

The measured flow rate provided by the sampler being assessed.

## Sampler Flow Units

Units code of target flow rate for the sampler.

## Sampler ID

The user assigned unique name or ID for the sampler at the site.

## Sampler Manufacturer

The name of the equipment manufacturer.

## Sampler Model Number

Manufacturer’s model number for the sampling instrument.

## Sampler Owner

Description/Name of the agency that owns the sampler

## Sampler Owner Code

Code representing the agency that owns the sampler.

## Sampler Serial Number

Manufacturer’s serial number for the sampling instrument.

## Sampling Begin Date

The earliest day that data exists for this monitor.

## Sampling End Date

The date on which a distinct period of operations (i.e., collection of air quality samples) stopped for the monitor.

## Sampling Schedule Offset

The offset from the EPA schedule baseline date (1/4/1956), i.e., 1/4/1956 + offset = the baseline date for this record's schedule

## Scale

The number of significant digits to the right of the decimal in value.

## Schedule Exemption Indicator

Indicates that the sampling schedule differs from that required by the standard, by approval of the Regional Administrator.

## Scheduled Day Count

Number of days scheduled for samples to be taken at the site during the time period (quarter or year). It is equal to the scheduled days (regardless of collection) for the primary monitor and the number of days for the duplicate samplers that were scheduled and collected.

## Scheduled Sample Count

The count of sample measurements that were taken on scheduled sample dates during the indicated time period (quarter or year).

## Scheduled Sample Date

The scheduled sample date for a monitor. If the sample is taken on this date, then it is creditable. (If a sample flagged as creditable is not on a scheduled date, then it is a valid make-up sample).

## Screening Group

Name of the Screening Group that the data is submitted for. This must be included with each AQS data submittal. A screening group is a set of monitors for which the same users have the same permissions. An agency may have one screening group or they may have many if they need to separate workflows.

## Second Max Date and Time

The date and time (on a 24-hour clock) when the second highest value for the year was taken.

## Second Max Value

The second highest value for the year.

## Second Non-Overlapping Max Date and Time

The date and time (on a 24-hour clock) when the second maximum non overlapping value for the year was taken.

## Second Non-Overlapping Max Value

For 8-hour CO averages, the second highest value of the year that does not share any hours with the 8-hour period of the first max non overlapping value.

## Secondary Exceedance Count

The number of samples during the year that exceeded the secondary air quality standard.

## Seventh Max Value

7th highest daily summary for year with the appropriate exceptional data type.

The street address giving an approximate location of the site.

## Site Established Date

The date when the monitoring site began operating.

## Site Evaluation by HQ Date

The date on which the most recent evaluation of the site for siting criteria by EPA headquarters (HQ) occurred.

## Site Evaluation by Region Date

The date on which the most recent regional evaluation of the site for siting criteria occurred.

## Site Number

The 4-digit number used to uniquely identify the air monitoring site within a state-county combination or tribal area. The values are always numeric, but are treated as a string and padded with leading zeroes so they always have 4 digits.

## Site Status

An indicator of the processing status of the site transaction within AQS. P indicates "production" and that all data has been screened and is ready for use. Any other status means the site data is still being entered or reviewed and the data should not be used.

## Site Terminated Date

The date on which the operating agency indicated that all operations ceased at this site.

## Sixth Max Value

6th highest daily summary for year with the appropriate exceptional data type.

## Spatial Average Indicator

Indicates whether spatial averaging is to be performed for the all-individual annual weighted means for sites that are flagged and in the same community-monitoring zone.

## Standard Deviation

The standard deviation about the mean of the values for the averaging period.

### Value Assignment

#### 1-Hour and 8-Hour Ozone

$$\sigma = \sqrt { \frac { (({v \cdot \sum_{i=1}^v d_i^2}) - ({\sum_{i=1}^v d_i})^2 } {v \cdot (v-1)} }$$

Where:
$$\sigma =$$ standard deviation
$$d_i =$$ percent difference (q.v.) of analytical or flow precision check
$$n =$$ number of checks

#### Non-Ozone NAAQS Durations

$$\sigma = \sqrt { \frac { (({n \cdot \sum_{i=1}^n s_i^2}) - ({\sum_{i=1}^n s_i})^2 } {n \cdot (n-1)} }$$

Where:
$$\sigma =$$ standard deviation
$$d_i =$$ percent difference (q.v.) of analytical or flow precision check
$$n =$$ number of checks
If the count of observations is 1, or the square root operand above is negative, the standard deviation is assigned a value of zero.

## Standard Exclusion Indicator

Set to 'Y' to indicate that the standard may be selected for exclusion.

## State Code

The FIPS code of the state in which the monitor resides.

## Submitting Agency

The name of the organization submitting the quality management plan

## Submitting Agency Code

Agency Code of the organization submitting the quality management plan

## Summary Criteria Met

An indication of whether the regulatory data completeness criteria for valid summary data have been met by the monitor for the year. Y means summary criteria exist for the parameter-duration and they were met; N means they exist and were not met; NULL (empty) means there are no summary criteria for the parameter-duration.

## Summary Method Count

The count of distinct methodologies that were used to collect and analyze the summarized samples during the time period represented (e.g., during the day or year).

## Summary Year

The calendar year represented by the aggregate statistics.

## Supporting Agency Code

The code of the agency assigned as "Supporting" for the monitor reporting data.

## Target Flow Rate Unit

Units of measure code of the target flow rate

## Third Max Date and Time

The date and time (on a 24-hour clock) when the third highest value for the year was taken.

## Third Max Value

The third highest value for the year.

## Time Zone

A standard time zone, as established by Section 1 of the Standard Time Act, as amended by Section 4 of the Uniform Time Act of 1966 (15 U.S.C. 261).

## Traffic Count

An estimate of the amount of daily traffic volume on the road.

## Traffic Source

The method by which the traffic count was obtained.

## Traffic Year

The year that the traffic count data represents.

## Transaction Type

Transaction type code. On an AQS text transaction, this field indicates the type of data contained in the recrod.

## Transfer Standard Level

Level 1, 2, 3, 4 transfer standard has to be equal or a higher number then the Authoritative Standard

## Transfer Standard Value 1 - 10

Measurement from the instrument being assessed. There are 10 fields available for repoting up to 10 values.

## Transfer Standard ID

Unique ID code (serial number) for the UV ozone transfer standard used during the calibration process.

## Tribal Code

The BIA code representing the tribe on whose land the monitoring site resides. This is an optional way of displaying data. A tribe may (or may not) chose to enter their site's geographic location data using tribal code (rather than a state and county code).

## Tribe

The BIA name of the tribe with responsibility for operating the monitor, reporting data, etc.

## Units of Measure

The unit of measure for all statistics on the same row. Every parameter has a standard unit of measure. Submitters are allowed to report data in any unit and EPA converts to a standard unit so that we may use the data in calculations.

## Units of Measure Code

A code representing the units of measure.

## Unrestricted Air Flow Indicator

An indicator of whether the flow of air in the vicinity of the monitor's probe is unrestricted by physical obstructions. Valid values: Y (for Yes), N (for No), or W (for Waiver).

## Upper Confidence Limit

The upper probability limit (95% confidence) of the compared percent differences.

## Urban Area

The urbanized area (population greater than 50,000) within which the monitoring site is located.

## Urban Area Code

A code representing the urbanized area within which the monitoring site is located. An urbanized area is a U.S. Census Bureau demographic entity that comprises a place and the adjacent densely-settled surrounding territory that together have a minimum population of 50,000 people.

## Urban Area Represented

The urbanized area from which the pollution concentrations originated (not necessarily the location of the monitor).

## Urban Area Represented Code

A code indicating the urbanized area from which the concentrations originated (not the location of the monitor).

## Valid Audit Count

The number of levels whose relative percent difference falls within the acceptable range.

## Valid Collocated Data Pair Count

The number of valid collocated value pairs recorded during the time period.

## Valid Day Count

The number of required monitoring days in the aggregation period (e.g., year) where the monitoring criteria were met. (Only applicable for criteria pollutants.)

### Value Assignment

#### 1-Hour and 8-Hour Ozone

The number of active days within the effective monitoring season when minimum daily criteria were met, i.e., the daily Summary Criteria Met value is “Y”.

#### Daily PM10

The number of valued strata in the year. (A valued stratum is where at least one observation is made on, or after, a scheduled day, but before the next scheduled day.)

#### Daily PM2.5

The sum of valued, scheduled sampling days, plus make-ups for missing scheduled days. A make-up day is a sample recorded in the same stratum as, or exactly seven days after, a missing scheduled sample. In both conditions, the make-up sample must occur within the same quarter as the missed sample. A maximum of five make-up samples are allowed per quarter. (References: EPA-454/R-99-008 Guide line on Data Handling Conventions for the PM NAAQS; Memorandum: February 3, 1999 Use of Make-Up Samples to Replace Scheduled PM Samples.)

#### 24-Hour PM2.5 and PM10

The number of valid 24-hour block Arithmetic Mean (NAAQS) values within the year.

#### Annual PM2.5

The sum of scheduled sampling days, plus make-ups for missing scheduled days for the year.

#### Site-Level Annual PM2.5

The count of scheduled days for available quarters where a site-level summary exists (of any type) plus count of make up days. (Note: This is not affected by the existence of data flagged for exceptional event exclusion.)

#### Site-Level Quarterly PM2.5

The count of scheduled days in the quarter where a site-level summary exists (of any type) plus count of make up days. (Note: This is not affected by the existence of data flagged for exceptional event exclusion.)

#### 1-Hour SO2

The count of Daily Summaries with corresponding pollutant standard and exceptional data type, where the summary criterion is met.

#### 1-Hour NO2

The count of Daily Summaries where the summary criterion is met.

#### All Others

This field is not calculated for other pollutant-duration combinations.

## Valid Months Count

The number of months whose data capture rate, expressed as a percentage and rounded to a whole number, is greater than or equal to, 75

## Valid Observations Count

The total number of observations that meet minimum threshold requirements.

## Validity Indicator

An indicator whether the calculated value meets all completeness criteria to be considered valid.

## Values Above Primary Standard

The number of samples in the summarized sample set that exceed the level of the primary standard. (Only applicable for criteria pollutants.)

## Values Above Secondary Standard

The number of exceedances of the corresponding secondary standard, if one is defined, in the aggregated data set.

## Weighted Arithmetic Mean

The weighted arithmetic mean for the sample values in the summarized sample set. (Only applicable to PM10 and PM2.5)

### Value Assignment

$$Mean_{wtd} = \frac{\sum_{i=1}^{q} u_i} {q}$$

Where:
$$Mean_{wtd} =$$ weighted arithmetic mean
$$q =$$ number of active quarters
$$i =$$ quarter
$$u_i =$$ arithmetic mean of samples in quarter i of appropriate exceptional data type

## Worst Site Type

Within a particular monitoring area, those monitors with the highest PM10 concentrations must have their worst site type set to 1, and are expected to monitor at the recommended collection frequency. Other monitors must be classified as either not worst site monitors or monitoring on an accelerated schedule, but not at the recommended collection frequency.

## Year

The year the data represents.

## Year Represented by Audit

The year represented by the audit. For a particular audit, indicates the actual dates (Year) in which the sample was collected. Valid values are in the format YYYY and must be less than or equal to the Accuracy Date's year.

The Year Represented is required only for lead (Pb) analytical audits performed in the laboratory to link the year to the concentration samples analyzed during the audits.

If the user does not enter a value for this field, then the system will generate a value for this field same as the Accuracy Date year.

## Zero Span Scale

The number of digits past the decimal used in reporting the Zero Span Value

## Zero Span Value

A monitor measurement recorded when sampling a gas with a zero concentration of the measured substance.

## Zip Code

The postal zip code in which the monitoring site resides.