Ask the Expert Question:
We have procured several PUF sample trains from TestAmerica to test for dioxins and furans using EPA Method TO-9a. The method specifies a usual sampling time of 24 hours to obtain a sample air volume of between 325 to 400 m^3. We will probably run our sampler no longer than 60 minutes with a total sample volume collected of about 20 m^3. The 60 minute sample time bounds the time frame of the emissions we are trying to measure. Any additional time could introduce the potential for confounding sources to be captured in the sampler. Is this a concern of running the sampler less than the "usual" 24 hours from a MDC perspective or is the 24 hours just a convention specified in the method?
Experts Response:
The time recommendations cited in the Method are for relative reference purposes only, and are called out to show the volumes collected over that period of time as examples. There should be no deleterious effects to smaller sample volumes aside from higher reporting limits. If reporting limits are an important issue to your project, and they cannot be obtained by your 60 minute duty cycle, then you should consider more sampling during operational times when correct conditions are regained. That’s how incinerators are tested after a malfunction. Nothing should logically prevent multiple-sampling cycles of your test conditions when they occur. Your custom sampling implementation could take into consideration startup and shutdown, as needed.
Please also note that we often prepare a different apparatus of sampling media for much smaller air volumes than collected on a standard Hi-Volume sampler. The ORBO (click here to see attached picture) is prepared for battery operated pumps, and could be put much closer to your sources. They are very easy to handle.
No comments:
Post a Comment