'k o the a/s thingie...
post sampling;
side a = sample side, inlet surface, aka dirty side.
side b = pump side, outlet surface, aka clean side.
read both side w/ frisker. if side a has a higher count rate, you have an excellent chance of alpha being present as alpha will not penetrate the paper, thus not being detected on the b side frisk. ratio the frisker values and compare against your radon ratio, if the ratios ~ match, you're seeing alot of radon and not much else.