Technology Transfer Network
Emission Measurement Center
Method 23 - Dioxins and Furans
FREQUENTLY ASKED QUESTIONS (FAQS) for Method 23
Method 23 requires me to rinse the glassware in the sampling train with acetone and methylene chloride and then perform a separate "quality assurance" rinse with toluene. The method requires that I keep the toluene rinse separate and analyze it separately. Can't I save some money by combining these rinses and analyzing them together?
The method is clear that the toluene rinse should be stored separately and analyzed separately. However, based on the information that we have collected using this procedure since Method 23 became final, we now know that the toluene rinse will not significantly increase the amount of recovered dioxins/furans. Therefore, it is appropriate to allow a laboratory to combine the toluene rinse with the methylene chloride/ acetone rinse so that they can save the analytical cost of an additional sample fraction. However, the combining of the toluene rinse with the methylene chloride/acetone rinse for analysis must be handled as a minor change to a test method. That means that the tester/source must make it clear in their test plan that they are making this change and that the responsible agency (typically the state, but sometimes the EPA Region) must approve the change before the tester/source proceeds.
For Method 23, do I need to correct the emissions results to 12 percent CO2?
We sometimes require that industries correct their emission data to a fixed CO2 or O2 concentration to prevent the industry from simply diluting their emission gases with ambient air to reduce the concentration of the measured pollutant. The CO2 or O2 concentration that they must use to correct their measured emissions is somewhat arbitrary, but requiring that everyone correct their results means that everyone will report their emissions on the same basis. Because the concentration used to correct the emission data may vary among different industries, the required correction is part of the emission limit rather than the test method.
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