The decrease in particles with the smoking ban doesn't prove or disprove what I'm asserting, which is that (a) bleed air into the cabin was reduced and (b) filters were replaced less often, after the tobacco ban. In fact, what I'm saying is that the airlines leveraged the tobacco ban and commensurate reduction in measurable PM(2.5) as a legal excuse to reduce filtration of air five-fold, resulting in much higher levels of viral particles recirculating.