Study to determine the effect of moisture on volatile organic compound recovery rates for thru-the-probe audits into stainless steel canisters
- California Environmental Protection Agency, Sacramento, CA (United States)
Thru-the-probe (TTP) audits of criteria pollutants allow us to check the integrity of the entire sampling and analysis phases of ambient air pollution monitoring. By auditing thru-the-probe we can detect not only problems associated with instrument calibration and operation, but also problems associated with the station probe line from leaks or contamination. In 1989 we expanded the TTP audit program to include the ambient toxic monitoring program. This field audit program joined an existing laboratory audit program for volatile organic compounds (VOCs). Using this approach we were able to determine the field and lab biases and identify areas for improvement in the network. Based on the TTP audits, the ARB conducted a two part canister comparison study to determine the effect of canister moisture on VOC recovery rates from stainless steel canisters. The results of the study will be used to determine the best auditing method for VOC recovery. In Part 1 of the study, we compared the results of standard gas administered into dry canisters with the results of wet injected canisters. The results confirmed improved sample recovery utilizing wet injected canisters for VOC sampling. Humidifying the sample canisters with high grade water improved recovery rates in eight out of 18 VOCs while using a pre-run zero air purge. In Part 2 of the study, wet injected canisters were compared with canisters humidified by adding moisture to the diluent zero air stream. Both audit procedures used a pre-run zero air purge. The humidified diluent ensured all components of the collection system were exposed to moisture prior to being combined with the audit gas and administered to the probe. This practice improved VOC recovery rates over the wet injected canister method in three out of 18 VOCs. This paper is a report on the results of the two part canister humidification study. 10 figs., 3 tabs.
- OSTI ID:
- 617638
- Report Number(s):
- CONF-9605175--
- Country of Publication:
- United States
- Language:
- English
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