The relevance of the fan with filter is that it is analogous to your lungs which can also trap radioactive particles, like radon, causing say lung cancer.
Yes, radon is a gas. Why did you bring this up? Were you implying that dust collection couldn't work? I can see why you might think that if you didn't understand that Radon is radioactive and has a short half-life (3.8 days).
> Most short term radon tests will use activated charcoal to absorb the radon gas in the air. Various short terms tests kits will include some type container filled with activated charcoal, usually perforated or screened and has a filter to keep out radon decay products. At the end of testing, the absorber is resealed and returned to the vendor for processing and evaluation.
> When radon undergoes radioactive breakdown, it decays into other radioactive elements called radon daughters (or progeny). Radon daughters are solids, not gases, and stick to surfaces such as dust particles in the air. Dust particles carrying radon daughters can move with air.