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innovative environmental solutions,inc.

Technical Memorandum

Date: August 11, 2009

To: Stephanie Meadows/API

Matt Todd/API

From: Tom McGrath

Subject: Review of Anomalous EPA Method 323 Formaldehyde Emission Measurements

Recent emission test results from EPA Region 8 have raised questions regarding the reliability of 

Method 323 “Measurement of Formaldehyde Emissions from Natural Gas-Fired Stationary Sources—

Acetyl Acetone Derivitization Method”. As a result, this Method was not included in the proposed 

revisions to the RICE NESHAP (40 CFR 623 Subpart ZZZZ) as an option for formaldehyde emission 

measurements. In the docket for the proposed rule, document EPA-HQ-OAR-2008-0708-0020.pdf

discusses questionable test results from the Conoco Philips Sunnyside and Argenta compressor 

stations. EPA Region 8 notes that the measured emissions are much lower than the engine rates

published by the engine manufacturer.

Method 323 withdraws a sample from the stack and “bubbles” that sample through an impinger train 

(i.e., specialized glassware) containing water. Formaldehyde is absorbed in the water, which is 

chemically treated and analyzed. Method 323 is an example of a “wet test method” and important 

sampling and analysis parameters for wet methods include the total sample volume, sample time, 

sample rate (volume divided by time), and amount (i.e., weight or mass) of the species collected. 

When reviewing test reports for wet methods, there are many test parameters, analytical results, and 

related calculations that warrant review. Sample rate, sample volume, and recovered mass of the 

subject species (i.e., formaldehyde for Method 323) are key starting points for the test report review. 

Innovative Environmental Solutions (IES) reviewed the subject emission test reports and determined 

that the sample rate during the tests was approximately an order of magnitude higher than the 

maximum sampling rate allowed by the test method (i.e., maximum rate of 0.4 liters per minute (lpm)

versus test rate of approximately 4 lpm). Because the sample rate was well above the method 

specification, it is very likely sample breakthrough occurred (i.e., formaldehyde was not completely 

absorbed in the impinger solution) and the measurements were biased low.

Select pages from the Argenta Compressor Station test report are included below and show the 

incorrect sample rate. Key data are labeled to facilitate presentation of the data from Run #1 on Unit 

E007. 

A – is the Run #1 sample volume = 0.227 m3 = 227 liters;

B – is the mass of formaldehyde measured in the Run #1 sample = 0.9078 mg;
Anomalous EPA Method 323 Measurements Review August 11, 2009

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C – is the calculated Run #1 stack concentration = 4.10 ppmv; 

D – is the Run #1 emissions reported in the summary of results = 4.10 ppmv; and 

E – lists the sample volume (0.227 m3

/227 liters) and the sampling stop and start time: 9:49 –

8:49 = 60 minutes which is the typical sample period for Method 323.

A sample rate of 227 liters/60 minutes = 3.8 liters per minute is calculated based on items A and E. 

This is about 10 times the maximum sample rate allowed by the test method (0.4 lpm). IES had 

follow-up conversations with test personnel to discuss whether data transcriptions could have occurred 

in the report – i.e., the sample volume and rate were different than reported. Those conversations 

confirmed the higher sample rate.

Similar data review and calculation for other test runs indicates that similar sampling rates were 

utilized for all test runs on all the tested units. Due to this sampling error, these measurements would 

be expected to result in formaldehyde emissions with a similar low bias. 
Anomalous EPA Method 323 Measurements Review August 11, 2009

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Anomalous EPA Method 323 Measurements Review August 11, 2009

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Anomalous EPA Method 323 Measurements Review August 11, 2009

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