That is what I have read, too, tho I cant remember where. It specifically mentions people w/asthma or a lung disease. I know someone who has asthma who has one in her bedroom and has had only good results. Better sleep, better breathing, less heart and asthma related night/early morning disturbances.

As w/any medicine one must exercise caution and good judgement. One size does not fit all. This device must be cleaned as frequently as needed (and I think each home is different in this respect: smoker/non-smoker, candles/no candles, carpeting/no carpeting. If one does not keep the device properly cleaned, the device will begin to emit the very toxic dust that it is there to eliminate. This is a machine where following the directions are simple, but crucial to its performance.