Method 3C
Determination of Carbon Dioxide, Methane, Nitrogen, and Oxygen From Stationary Sources
40 CFR Part 60, Appendix A-2
From the method — regulatory text
Sections 1 and 2 of Method 3C—Determination of Carbon Dioxide, Methane, Nitrogen, and Oxygen From Stationary Sources, as published at 40 CFR Part 60, Appendix A-2. Retrieved 10/07/2026. The full method is on the eCFR.
1. Applicability and Principle
1.1 Applicability. This method applies to the analysis of carbon dioxide (CO2), methane (CH4), nitrogen (N2), and oxygen (O2) in samples from municipal solid waste landfills and other sources when specified in an applicable subpart.
1.2 Principle. A portion of the sample is injected into a gas chromatograph (GC) and the CO2, CH4, N2, and O2 concentrations are determined by using a thermal conductivity detector (TCD) and integrator.
2. Range and Sensitivity
2.1 Range. The range of this method depends upon the concentration of samples. The analytical range of TCD's is generally between approximately 10 ppmv and the upper percent range.
2.2 Sensitivity. The sensitivity limit for a compound is defined as the minimum detectable concentration of that compound, or the concentration that produces a signal-to-noise ratio of three to one. For CO2, CH4, N2, and O2, the sensitivity limit is in the low ppmv range.
EssentialRegs notes
Our plain-English reading of Method 3C. Not the method text.
What it measures
The concentrations of carbon dioxide, methane, nitrogen and oxygen in a gas sample.
How it works
A gas sample is collected in a bag or other container and injected into a gas chromatograph, which separates the gases as they pass through packed columns. A thermal conductivity detector responds to each gas as it leaves the column, and the instrument is calibrated with gases of known concentration. The method is written for gases such as landfill gas and vent gas, where methane is a major component and the gas is not a combustion exhaust.
Equipment
A gas chromatograph with a thermal conductivity detector and separation columns, a sample collection bag or container, and calibration gases of known concentration.
When a rule cites it
Gas composition for landfill gas and for vent gas and similar process streams where methane, carbon dioxide, nitrogen and oxygen need to be quantified. It is invoked when a rule needs a gas analysis and the stream is not a combustion exhaust that Method 3 or 3A could read.
Notes for compliance staff
Samples are collected in a container and analyzed in a laboratory or in the field, so the time between collection and analysis and the container handling belong in the report. Methods 3, 3A and 3B are written for combustion-type gases and do not report methane.
Cited by
Provisions in the corpus whose text cites Method 3C. Subscribers land on the provision in the regulation reader; visitors see a preview of it (the GP05 sample opens in full).
40 CFR Part 60 Subpart OOOO
40 CFR Part 60 Subpart OOOOa
40 CFR Part 60 Subpart OOOOb
40 CFR Part 60 Subpart OOOOc
The sections marked as regulatory text above are reproduced from the CFR. Everything under ‘EssentialRegs notes’ is our reference copy, not the method. The method as published in the CFR controls.