When is it appropriate to request air testing canisters to be filled with helium?
A. Canisters may be backfilled with helium (prior to sampling) if you are sampling landfill gas that is expected to have high hydrogen sulfide and/or methane levels. The dilution of the sample will potentially bring concentrations of H2S/CH4 under the levels deemed hazardous by DOT. Backfilling is only performed upon request from the client.
