Humidifiers: How to Use and Maintain Them

What Is a Humidifier?

A humidifier puts moisture into the air. That can be especially helpful in winter, when the weather and indoor heating systems can make the air dry -- and dry out your eyes, nose, lips, and skin.

You should aim for 30% to 50% humidity in your home. You can measure the level with a tool called a hygrometer that’s available at most hardware stores. Consider a humidifier if your level is below 30%, especially if you often have a sore throat, bloody nose, or dry skin.

Once you have a humidifier in place, it’s still important to keep an eye on the humidity levels. Anything above 50% can be a breeding ground for bacteria, fungi, and other germs. Higher than 60% can lead to condensation on windows and other surfaces, which also invites microorganisms into your home.

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Some humidifiers have a humidistat that senses the humidity in the room and shuts the machine off when it hits the right level.

Humidifier Benefits

Parched air draws fluid from your sinuses, which can make you more likely to have nosebleeds or sinus infections. Along with helping prevent those things, a humidifier also may make it easier to breathe if you have a cold or another condition that affects your lungs.

Humidifiers also may help with the following:

Dry or irritated eyes

Dry skin

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Dry cough

Sore throat


Types of Humidifiers

Vaporizers work the same way as a pot of water on the stove. They boil water to make steam, and it evaporates into the air. Some doctors warn against using these if you have children because of the risk of burns.

Evaporative humidifiers use a fan to blow air over a wet, absorbent material like a wick that sends moisture into the air. Not only is it simple and relatively safe, but it’s also less likely than other types of humidifiers to release bacteria and minerals into the air. But that’s only if you regularly clean and dry it and change the filters.

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Central humidifiers are connected to your house’s plumbing and heating and air conditioning, and they cover the entire house. It’s convenient because you don’t have to refill the water supply, but you do need to maintain the system well to keep certain allergens from getting into the air.

Ultrasonic humidifiers use super-fast vibrations to turn water into vapor. These are quiet, efficient, and they don’t cost a lot.

Impeller humidifiers have a disk that spins at high speed and turns water into vapor.

What Kind of Water to Use

Tap water has different amounts of minerals, depending on where you live. They can gum up your humidifier and breed bacteria that get spewed into the air along with water vapor. The minerals also can form a fine white powder that can lead to crusty deposits in the machine -- another breeding ground for bacteria. These issues are more common with ultrasonic and impeller humidifiers.

Distilled water, available in grocery stores, has fewer minerals, but it’s not clear that it’s any better than tap water as long as you clean your humidifier regularly.

Humidifier Risks

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While humidifiers can be helpful in lots of ways, it’s important to keep them clean and well-maintained. A dirty humidifier can be a breeding ground for bacteria and mold, and if they start growing in a humidifier, they get sent out into the air and you can breathe them in. The same goes for the tiny minerals in bottled or tap water.

And don’t let the air get too humid -- that can lead to condensation on walls and floors and become a home for bacteria, mold, and dust mites. These can trigger allergies and be especially harmful if you have problems with your breathing, like asthma. An air conditioner or dehumidifier can help even humidity out.

Be especially cautious if you have a steam-based humidifier, which boils water. They get really hot and can cause burns if they’re not handled carefully.

Cleaning Your Humidifier

It’s best to clean your humidifier at least once a week:

Always unplug your humidifier before you clean it. Water and electricity can be dangerous together.

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Empty, rinse, and dry the base and tank every day.

Once a week, get rid of any mineral buildup with vinegar or another solution suggested by the manufacturer, and disinfect the humidifier with a 10% bleach solution (follow the instructions for your specific model). Be sure to rinse the tank with several changes of water if you use bleach or any other cleaning chemicals so the machine doesn’t put them into the air next time you use it.

Check your filters or cartridges regularly, and change them according to the manufacturer's instructions.

Do all these steps right before you store your humidifier and just after you take it out of storage to use it again, too.

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