With the recent revisions to Method 202 for condensable particulate matter (CPM), the US EPA included an exception to the requirement to extract the CPM filter (the secondary filter that is located between the “warm” and “cold” sections of the impinger train). The exception is subject to the following conditions:
1. The source temperature is less than 85°F;
2. Sampling is done using an in-stack filter (Method 17 or Method 201A)
3. The analytical laboratory is able to obtain a stable weight for the CPM filter (suggesting a lack of high vapor pressure sulfate species).
Sampling for CPM under essentially ambient stack conditions is somewhat unusual, and is not something the analytical laboratory is likely to expect. Testers collecting samples under these circumstances should take care to notify the laboratory, both on the chain of custody and by way of a separate note or phone call.