Hi here are my responses to your questions:
What do you class as the sampling area? – we take one FB to the sampling area, exposed briefly inside the enclosure before sampling or one FB is taken to one location if air testing in a number of locations.
How are each of you interpreting this line? Specifically the word “job” – we interpret that to be each sampling session. Normally, if we are on site for the day we will allocate one FB or if we are sampling in two separate locations, say one morning and one afternoon, we would have two FBs.
Reason for FB – to ensure that during preparation for sampling that we have not contaminated the filter. e.g. If an enclosures fails Stage 3 air testing, then the FB will confirm that the analyst did not contaminate the filter, it was a ‘dirty’ enclosure.