An important element in emission control technology design and implementation is the utilization of reference test methods used to evaluate equipment performance.  Universal acceptance of the validity of such methods is essential to the proper functioning of the commercial marketplace for emission control systems; i.e., customers want to know that the equipment being acquired really works.

Since the passage of the original Clean Air Act in 1970, the United States Environmental Protection Agency (EPA) has led the way in researching and promulgating formal test methods directed toward satisfying this need.  These EPA methods for quantifying a wide variety of pollutants from point, fugitive, and mobile sources as well as ambient air, are accepted around the world by many countries as the reference standards.  The complete list of all promulgated and pending test methods is voluminous and can be found here:
In addition, the promulgated methods that are specific to air emission measurements can be found here:

Within this list of air emission test methods, there are several methods that are commonly relevant to the design and implementation of air pollution control systems.  A brief summary of each of these follows.  Note that many of these have related methods (i.e., Methods 5A, 5B, 5C, etc.) that are designed for specific stack sampling situations.

Gas Velocity and Flow

Methods 1 & 2

Prescribes the way a duct or stack should be traversed using a pitot tube to measure velocity pressure to calculate velocity and flow rate.

Molecular Weight of Stack Gases

Method 3

Provides for the measurement of CO2 , O2 , N2 with an Orsat apparatus.

Water Vapor Content

Method 4

Utilizes a wet condensation extractive technique to quantify the amount of water vapor in a gas stream.

Particulate Matter

Method 5

Determines the concentration of filterable particles in the gas stream by an extractive, gravimetric method.

Sulfur Dioxide

Method 6

Utilizes a wet chemical, titrimetric, extractive method for SO2 concentration.

Nitrogen Oxides

Method 7E

Utilizes a continuous on-line analyzer to determine both NO and NO2 concentrations.

SO3 and Sulfuric Acid Mist

Method 8

Utilizes an extractive, titrimetric method for SO3/H2SO4.


Method 9

Relies on the observations of a trained individual to quantify plum opacity.

Particulate Matter (PM)

Method 17

Utilizes an in-stack filter to gravimetrically quantify the filterable PM at stack conditions.

Volatile Organic Compounds (VOCs)

Method 18

Utilizes a grab sample with off-line gas chromatography to characterize the VOCs in the gas stream by species.

Volatile Organic Compounds (VOCs)

Method 25A

Utilizes a continuous, on-line flame ionization detector to quantify VOCs as propane or carbon.

Condensable Particulate Matter

Method 202

An extractive method that provides for the quantification of condensable PM that is not caught on a filter. This method is generally coupled with Method 5 or 17 which provide for the filterable portion of the sample.

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