This practice presents the procedures and equipment that will permit, within certain limits, representative sampling of stationary source emissions for the automated determination of gas concentrations of effluent gas streams. This application is limited to the determination of oxygen (O₂), carbon dioxide (CO₂), carbon monoxide (CO), sulfur dioxide (SO₂), nitric oxide (NO), nitrogen dioxide (NO₂) and total oxides of nitrogen (NO_x). Although velocity measurements are required to determine the mass flow rates of gases, this is, however, not included in this practice. This practice describes representative sampling of gases in a duct, both by extractive and non-extractive methods. In extractive sampling, gases are conditioned to remove aerosols, particulate matter, and other interfering substances before being conveyed to the instruments. In non-extractive sampling, the measurements are made in-situ; therefore, no sample conditioning except filtering is required.

1.1 This practice² covers procedures and equipment that will permit, within certain limits, representative sampling for the automated determination of gas concentrations of effluent gas streams. The application is limited to the determination of oxygen (O₂), carbon dioxide (CO₂), carbon monoxide (CO), sulfur dioxide (SO ₂), nitric oxide (NO), nitrogen dioxide (NO₂) and total oxides of nitrogen (NO_x).

1.2 Velocity measurements are required to determine the mass flow rates of gases. This is not included in this practice.

1.3 There are some combustion processes and situations that may limit the applicability of this practice. Where such conditions exist, caution and competent technical judgment are required, especially when dealing with any of the following:

1.3.1 Corrosive or highly reactive components,

1.3.2 High vacuum, high pressure, or high temperature gas streams,

1.3.3 Wet flue gases,

1.3.4 Fluctuations in velocity, temperature, or concentration due to uncontrollable variation in the process,

1.3.5 Gas stratification due to the non-mixing of gas streams,

1.3.6 Measurements made using environmental control devices, and

1.3.7 Low levels of gas concentrations.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For more specific safety precautions, refer to 5.1.4.8, 5.2.1.6, and 6.2.2.1.