Consumer Reports did a study on humidifiers, an appliance many of us need during winter when the inside air is very dry. They determined that too many humidifiers push a lot of bacteria into the air which in turn makes many of of sick. Humidifiers with antimicrobial claims weren't necessarily any better at preventing bacterial growth or emitted bacteria. And, of course time gets by us and we don't get around to cleaning them often enough to prevent the bacteria. So what type is best?
It was found that none of the 10 evaporative wick models emitted any bacteria. This type will blow air over a wet wick filter, a filter which looks like this:
However, there is always a codicil and it is that in the case of safe humidifiers, :the safest approach is to empty, rinse, and dry it out every day. And once a week follow the manufacturer's instructions on how to disinfect the tank.
Kind of makes you paranoid, eh?