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EPA PAMS Re-engineering

Posted: Wed Dec 09, 2015 6:14 pm
by Mad Hatter
The EPA started a project to re-engineer the PAMS Network back in 2011.  The initial stages included a review by the Clean Air Scientific Advisory Committee (CASAC) Air Monitoring and Methods Subcommittee (AMMS) of the current PAMS program and resulted in additional presentations at the NACA Monitoring Steering Committee Meeting in July, 2012 outlining network changes which resulted in recommendations which have in part been implemented in the new NAAQS rules.

http://www3.epa.gov/ttnamti1/pamsreeng.html

Previously agencies required to participate in the PAMS network were given the option to monitor VOC's by either continuous methods like AutoGC, or canister collections.  The network re-design calls not only for a re-distribution of monitoring activities but also for more continuous measurements.  In conjunction with the network re-design, the EPA began a project to evaluate the current technologies for continuous field VOC measurements.  This activity was to be divided into a laboratory evaluation of available technology and then a field study of those instruments which performed well in the laboratory phase.  The Laboratory Evaluation report was published in October, 2014.  The Lab study included 8 different AutoGC systems and although three were chosen for the field study by the EPA additional participants were allowed to contribute their hardware based on their performance and motivation. 

Re: EPA PAMS Re-engineering

Posted: Wed Dec 09, 2015 6:17 pm
by White Queen
As with the lab study, the field study is being implemented by RTI International and EC/R Incorporated and while the lab study was not without challenges, the field study has proved to be plagued with problems.  The original plan for the field study called for systems to be implemented into a monitoring trailer and then over a period moved to three locations around the county to collect data for 30-45 days at each site.  Instrument manufacturers were to provide standard operating procedures from which RTI operators could run the instruments for the evaluations. Six instruments are currently in the field study and needless to say, putting 6 systems into a single monitoring trailer was overly optimistic.  It quickly became apparent that the tear-down, setup aspects of moving the trailer to multiple sites was not feasible.

Re: EPA PAMS Re-engineering

Posted: Wed Dec 09, 2015 6:18 pm
by Duchess' Cat
The field site has been plagued with issues which are not new to monitoring stations but have been exacerbated by the attempt to run so many systems in a single trailer.  A/C failures, power issues and problems with air and support gas supplies have caused constant delays and last but not least has been problems with sample lines.  With so many systems in a single trailer the sample manifold simply cannot be realistically located close to each system.  This has resulted in some systems being within several feet of the manifold supplying samples and others being more than 15 feet away.  Initial testing with 1/8" SS lines resulted in some instruments (likely the farthest) not getting all targets or having carry-over.  The problems were magnified by not having sufficient power to heat sample lines.  It was determined to fairly test all systems that all sample lines should be the same.

Re: EPA PAMS Re-engineering

Posted: Wed Dec 09, 2015 6:23 pm
by Red Queen
Currently the project is still working on getting a sampling strategy which works for all.  In Texas we use 1/8" SS lines which are heated to about 25-30C.   This is partly a result not so much from any intense study of the requirements as from the fact that the original PAMS Technical Assistance Document published by the EPA back in 1998 recommended this sampling strategy.  The typical sampling issues encountered in this analysis include getting low blanks, no carry-over after running quality control checks and getting good recoveries on quality control checks.  It is clear from current VOC sampling and testing that humidification of VOC samples is a critical aspect for sampling as well as generating good quality control samples in canisters.  Humidification can also affect sampling system blanks.  On our systems we can get excellent blanks on dry zero air but as soon as the sampling system is exposed humidified air the blanks will show higher levels for species of higher boiling points.  Likewise, in areas of low ambient humidity we see problems with recoveries on quality control checks.  Humidification is difficult to control and too much can also result in issues particularly in air conditioned trailers and heating lines reduces the potential for condensation to occur in lines when ambient humidity goes up.

I recently tested some sulfinert sample lines for use in the EPA study. Because of the number of instruments and varying distances from the manifold it was decided that everyone would use 16' x 1/8" lines and because of limited power resources in the trailer with 6 instruments they will be unable to heat the lines. When I tried this strategy on chromatography grade SS I had losses of heavies and carry-over of the lost heavies into as many as three additional samples. We don't see this on heated lines and must condition our heated lines for several weeks to get good reproducible sampling. I switched to the sulfinert and this was not a problem even with un-heated lines.

Re: EPA PAMS Re-engineering

Posted: Wed Dec 09, 2015 6:32 pm
by Mad Hatter
Has anyone used teflon lines? I think RTI started with SS and had problems and went to 1/4" teflon and it was working.

Re: EPA PAMS Re-engineering

Posted: Mon Jun 12, 2017 5:15 pm
by Red Queen
Field study results are now available on the EPA site:

https://www3.epa.gov/ttnamti1/pamsreeng.html