Brief Introduction of EPA Method 25  

Use for the determination of total gaseous non-methane organic emissions (TGNMO) as carbon.


Samples are collected in a precleaned and evacuated SUMMA canister or in a Tedlar bag using a pump. Composite samples may be collected using time-integrated sampling. Sample volume ranges from 1 to 20 liters. Ambient sampling will not be affected by humidity or rain.


The sample is analyzed by GC/TCD/FID. The GC/TCD/FID combination will measure both fixed gases (such as oxygen, nitrogen, carbon monoxide, carbon dioxide and methane by TCD) and NMHC (non-methane hydrocarbon by FID). A catalyst is used to convert all the NMHC to carbon dioxide followed by the carbon dioxide being converted to methane to be detected by the FID.


Canisters, Tedlar bags, GC/TCD/FID

Detection Limits

1.0 ppbw


One sample collected for all analysis. One injection will allow reporting of all analytes.


Actual run time is lengthy. The conversion catalyst is easy to burn out and is very expensive. The two conversion will decrease the accuracy of the analysis.


TO-14 modified, ASTM 1945, TO-3 modified

Representatives Uses

Landfill well gas surveys, ambient air surveys, manufacture emission gas surveys, indoor air, stack gas analysis.


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