Off-topic: Smoggy Days--why stay inside?
I've lived in some towns with poor air quality. Whenever especially bad air quality is forecast, the authorities advise susceptible people to remain indoors. Does anyone know why? Most homes exchange air with the outside in copious quantities (all the air volume in the home exchanged several times per hour). Few homes have filtration systems capable of getting rid of particulates that are really dangerous, and none can filter out noxious gasses. I've got to think composition of the air inside is virtually identical to the air outside. Plus, most homes have internal sources of air pollutants that significantly degrade air quality.
Still, the advice seems to be universal, so I must be missing something. Any ideas or guesses?