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Is it Safe? Humidifiers

February 16, 2015

Q: My child has chronic bronchitis and we have a humidifier in his room to keep his airways moist. However, I am worried about bacteria growing in the water as it sits there for days. Would these bacteria get into his bedroom air? Should I be using a disinfectant in the humidifier water?

A; First off, you are correct to be using a humidifier this time of the year. The home’s heating system dries out your indoor air and that can irritate the nose and lungs, which may make chronic bronchitis even worse. And yes, you don’t want bacteria, algae or anything else to grow in the humidifier reservoir as that could become airborne and be inhaled by your son.

However, humidifier disinfectants that are added to the water as bacteriostatic agents (keeping bacteria from growing) are not necessarily a good idea. Various types are marketed as liquid additives for humidifier reservoirs. The chemical disinfectants are potentially irritating to the lungs and will be pumped into the air with the water. An outbreak of very serious lung disease occurred in Korea from certain types of humidifier disinfectants that are not commonly marketed in the United States.

To play it safe, the best way to keep microbes from building up in the water is to discard the reservoir every morning, replacing with fresh water. Do a thorough cleaning every two or three days with soap and water; you can use a mild disinfectant such as vinegar to wipe down the humidifier parts when doing this cleaning, but harsh disinfectants such as bleach are not necessary. Make sure you rinse well before putting the humidifier back together.

Dr. Gary Ginsberg is a public health toxicologist in Connecticut and a lecturer at the Yale School of Public Health. He has written a book geared toward the general public, “What’s Toxic, What's Not,” and also has a website,, to answer questions about chemicals found in consumer products and in our homes.

The Yale School of Public Health invites you to submit questions for Dr. Ginsberg as part of this recurring monthly series. Contact us through Facebook or by e-mailing Michael Greenwood at

Submitted by Denise Meyer on February 17, 2015