Consumer Reports: Bacteria-breeding humidifiers

With winter's drier air, people start using humidifiers.

Manufacturers recommend cleaning them every day. But according to an informal Consumer Reports' poll, one in four people admitted to cleaning their humidifier only once a month or even less. Consumer Reports' latest research finds bacteria can grow fast - putting your health at risk.

You expect a humidifier to add moisture to the air, but if you don't clean it often enough, it could be adding more than that.

"Well, a dirty humidifier can emit bacteria into the air, and that could be a problem for people with asthma or allergies, and it can cause flu-like symptoms," said Dory Sullivan, Consumer Reports.

Many manufacturers make antibacterial claims like "produces pure bacteria-free vapors," "germ-free mist," and "antimicrobial material." Consumer Reports took a closer look at 35 humidifiers in three categories - vaporizers, which emit steam, ultrasonic humidifiers that release a fine mist into the air and evaporative humidifiers, which blow air over a wet wick filter.

Over the course of three days, testers measured the microbial growth in the humidifiers' tanks. In a second test they added bacteria to each tank and measured whether any
bacteria came out in the humidifier's mist.

"Humidifiers with antimicrobial claims weren't necessarily any better at preventing bacterial growth or emitted bacteria," Sullivan said.

What did make a difference in Consumer Reports' tests is the type of humidifier. All of the ultrasonic humidifiers and all but one of the vaporizers emitted some bacteria. But none of the 10 evaporative wick models emitted any bacteria.

With any type of humidifier, 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.

Consumer Reports says if you have an infant or suffer from asthma or allergies consider the Vicks Warm Mist Vaporizer for $15, or for larger rooms, the Honeywell evaporative humidifier for $60. Neither grew or emitted bacteria in Consumer Reports tests.

You can get more advice on buying a humidifier by going to

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