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APPENDIX C

PM2.5 Continuous Monitor Comparability Assessment and Request 

for Waiver

Introduction

The SCAQMD monitoring program has historically operated PM2.5 continuous monitors 

primarily to support forecasting and reporting of the Air Quality Index (AQI). These monitors 

supply data every hour to update the AQI on our web site as well as national web sites such as 

AirNow (www.airnow.gov). SCAQMD has been using these monitors since the early part of the 

last decade as the PM2.5 monitoring program was implemented. Over the last few years, a 

number of PM2.5 continuous monitors have been approved as Federal Equivalent Methods 

(FEMs). By utilizing an approved FEM, any subsequent data produced from the method may be 

eligible for comparison to EPA’s health based standard known as the NAAQS. The primary 

advantage of operating a PM2.5 continuous FEM is that it can support the AQI, while also 

supplying data that are eligible for comparison to the NAAQS. Thus, a network utilizing PM2.5

continuous FEMs can potentially lower the number of filter-based FRMs operated in the 

network, which are primarily used for comparison to the NAAQS. These filter-based FRMs are 

resource intensive in that they require field operations as well as pre- and post-sampling 

laboratory analysis which results in data not being available for approximately 2-4 weeks after 

sample collection. 

The SCAQMD monitoring program has been evaluating PM2.5 continuous FEMs over the past 

several years. Although the PM2.5 continuous FEMs are automated methods, these methods still 

require careful attention in their set-up, operation, and validation of data. Once enough data was 

collected, we began to evaluate the performance of these methods compared to collocated FRMs. 

That evaluation is explained further below and includes our request regarding the use of the data 

from these methods.

Request for Exclusion of PM2.5 Continuous FEM data from Comparison to the NAAQS 

The network technical requirements for requesting exclusion of data from comparison to the 

NAAQS are identified in 40 CFR §58.11(e). These requirements refer to the performance criteria
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described in Table C-4 to subpart C of part 53. To accommodate the differences in how routine 

monitoring agencies operate their networks, several additional provisions are described in 

§58.11(e). When a topic is not addressed in §58.11(e), then the test specifications from table C-4 

applies. 

As shown in the Table below, the slopes of the regression between collocated FRM and FEM 

measurements at the Anaheim, Central Los Angeles, North Long Beach, South Long Beach, and 

Rubidoux (POC 3) stations are higher than 1.1, which is outside the test specification indicated 

in §53 Table C-4 (i.e. slope = 1 ± 0.1). Although the slope criteria was met, the intercept of the 

regression relationship between FRM and FEM data at the Burbank, Rubidoux (POC 9) and 

Mira Loma monitoring sites does not meet the test specifications of between 15.05 - (17.32 × 

slope), but not less than -2.0; and 15.05 - (13.20 × slope), but not more than +2.0 (also indicated 

in §53 Table C-4).

Thus, in accordance with the PM NAAQS rule published on January 15th, 2013 (78 FR 3086) 

and specific to the provisions detailed in §58.10 (b)(13) and §58.11 (e), SCAQMD is requesting 

that data from the all of the SCAQMD FEM PM2.5 monitors be set aside for comparison to the 

NAAQS. While SCAQMD is working to optimize the monitoring instrumentation to meet all of 

our monitoring objectives, the performance is not yet at a point where the comparability of the 

PM2.5 continuous FEMs operated in our network compared to collocated FRMs is acceptable. 

After assessing the comparability of the PM2.5 FEMs to the collocated FRMs for our network, 

the sites listed below do not meet the comparability requirements. Detailed one-page assessments 

from which the information described below was obtained are included at the end of this section.
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Table – Request for Exclusion of PM2.5 Continuous FEM Data

Site Name City Site ID Cont 

POC

Cont

Method Description

PM2.5 

Cont 

Begin 

Date

PM2.5 

Cont 

End 

Date

Continuous/ 

FRM 

Sampler 

Pairs Per 

Season

Slope 

(m)

Intercept 

(y)

Meets Bias 

Requirement

Correlation 

(r)

Sites with PM2.5 continuous FEMs that are collocated with FRMs

Anaheim Anaheim 06-059-

0007 3

Met-One BAM 

1020 w/VSCC

01/01/

2012

12/31/

2014

Winter = 246

Spring = 251

Summer = 229

Fall = 259

Total = 979

0.99 4.66 No 0.87

Burbank Burbank 06-037-

1002 3

Met-One BAM 

1020 w/VSCC

01/01/

2012

06/30/

2013

Winter = 250

Spring = 236

Summer = 187

Fall = 172

Total = 845

1.05 5.24 No 0.88

Central Los 

Angeles

Los 

Angeles

06-037-

1103

3

Met-One BAM 

1020 w/VSCC

01/01/

2010

09/29/

2011

Winter = 138

Spring = 75

Summer = 95

Fall = 90

Total = 398

1.27 1.35 No 0.90

9

Met-One BAM 

1020 w/VSCC

10/01/

2012

12/31/

2014

Winter = 247

Spring = 244

Summer = 237

Fall = 236

Total = 964

1.16 5.12 No 0.84

North Long 

Beach

Long 

Beach

06-037-

4002 3

Met-One BAM 

1020 w/VSCC

01/01/

2011

09/30/

2013

Winter = 214

Spring = 228

Summer = 255

Fall = 175

Total = 872

1.16 2.23 No 0.94

South Long 

Beach

Long 

Beach

06-037-

4004 3

Met-One BAM 

1020 w/VSCC

01/01/

2012

12/31/

2014

Winter = 195

Spring = 251

Summer = 223

Fall = 189

Total = 858

1.25 0.50 No 0.93
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Riverside/

Rubidoux Rubidoux 06-065-8001

3

Met-One BAM 

1020 w/PM2.5 SCC

01/01/

2012

01/31/

2014

Winter = 256

Spring = 248

Summer = 260

Fall = 257

Total = 812

1.12 2.86 No 0.62

9

Met-One BAM 

1020 w/VSCC

01/02/

2012

12/31/

2014

Winter = 233

Spring = 237

Summer = 260

Fall = 253

Total = 983

1.03 3.43 No 0.86

Mira Loma Mira Loma 06-065-

8005 3

Met-One BAM 

1020 w/VSCC

01/01/

2012

12/31/

2014

Winter = 262

Spring = 253

Summer = 252

Fall = 248

Total = 1015

1.02 4.59 No 0.90
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Period of Exclusion of Data from the PM2.5 Continuous FEMs 

The above table details the period of available data by monitor on which the request to exclude 

PM2.5 continuous FEM data is based. Per EPA Regional Office approval, these data will be 

entered into EPA’s AQS database in a manner where the data are only used for the appropriate 

monitoring objective(s) (i.e., use data for just the AQI). Additionally, SCAQMD will continue to 

load any new data generated for the next 18 months (intended to represent the period until 

December 31 of 2016) in the same manner or until such time we request and receive approval 

from the EPA Regional Office to change the status of these monitors. 

PM2.5 Continuous FEM data for Reporting the AQI

While the analysis supports the request for the monitors above not be used for comparison to the 

NAAQS, the data are of sufficient comparability to collocated FRMs that they be used for public 

AQI reporting. Therefore, with EPA Regional Office approval we will report these data on our 

web site and to AIRNow (www.airnow.gov). As such, data submitted to EPA’s AQS database 

will be under “acceptable AQI” reporting (i.e., parameter code 88101) so that data users will 

know that these data are appropriate for use in AQI calculations, but not NAAQS comparison. 

Assessments

The following one-page assessments are locations where our agency has collocated PM2.5 FRM 

and continuous FEM monitors. Each of these assessments is represented in the “Table –

Request for Exclusion of PM2.5 Continuous FEM Data” above.
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Anaheim 

(FRM POC: 1; FEM POC: 3)
C-6

Burbank

(FRM POC: 1; FEM POC: 3)
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Central Los Angeles

(FRM POC: 1; FEM POC: 3)
C-10

Central Los Angeles

(FRM POC: 1; FEM POC: 9)
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North Long Beach

(FRM POC: 1; FEM POC: 3)
C-12

South Long Beach

(FRM POC: 1; FEM POC: 3)
C-13

Rubidoux

(FRM POC: 1; FEM POC: 3)
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Rubidoux

(FRM POC: 1; FEM POC: 9)
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Mira Loma

(FRM POC: 1; FEM POC: 3)