Air filter to catch radioactive particles - suggestions please

Having used the Corentium Canary for a four days in two different locations I think I can draw preliminary comparisions with my air filter tests.

1. Upstairs, well-ventilated office - 18 Bq/m3 and 2-3 times above background on the air filter, with the occasional "hotspot" detected by my SBT-9

2. Basement, poorly-ventilated tool room - 244 Bq/m3 and about 30 times above background on the air filter as detected by my SBT-9

Radon is present because the Canary is only looking for 222-Rn. Due to being a Noble gas, the Radon shouldn't accumulate to any degree on the air filter, but the decay progeny should as these are charged metals. The radioactivity decays fairly rapidly over the course of a day or so until background readings are detected on the air filter again. I think the main progeny involved are 218-Po, 214-Bi and 21- Pb which have half lives of 3, 20, and 27 miinutes, but only a proper laboratory analysis of the airfilter could confirm this.