Comparison of Gas Sampling Bags to Temporarily Store Hydrogen Sulfide, Ammonia, and Greenhouse Gases

Abstract

The National Air Emission Monitoring Study (NAEMS) project measured gas concentrations using automated semi-continuous gas analyzers. An alternative gas sampling technique is to use portable systems to fill 50 L gas sample bags over 24 h sampling periods and measure gas concentrations later in the laboratory. For this technique, a gas sampling bag that can retain gases over 24 h is needed. The objective of the study was to assess the impact of initial gas concentrations (low, medium, and high) and storage times (2, 6, 12, 24, 36, 48 h) on hydrogen sulfide, total reduced sulfur (TRS), ammonia, methane, and nitrous oxide stability in Tedlar and FlexFoil bags. Average gas concentrations ranged from 771 to 2,655 ppb, from 782 to 2,750 ppb, from 657 to 1,997 ppb, from 10,441 to 13,803 ppb, and from 337 to 344 ppb for H2S, TRS, NH3, CH4, and N2O, respectively. Bag reusability and background contamination were also investigated. Percent recoveries from FlexFoil bags ranged from 75% to 99.5% for all gases and concentrations except for TRS at high concentrations. For TRS at high concentrations, percent recovery from FlexFoil bags was 68.8%. No gas desorption or permeation was observed when using new FlexFoil bags. FlexFoil bags were more durable than Tedlar bags to mechanical stress and aging effects. There was no need to use a cover for FlexFoil bags to protect samples from sunlight. The cost of FlexFoil bags was lower than that of Tedlar bags.