A recent tragedy in South Korea illustrates the potential danger of improperly maintained humidifiers. At least 95 people were killed and hundreds more injured by inhaling a commonly available toxic chemical disinfectant for humidifiers. Even more recently in Southern California, the family of a woman filed suit claiming she died after exposure to the same chemical from a humidifier. While cases like these make headlines, there are no exact numbers on how many people in the U.S. get sick every year as a result of improperly maintained portable humidifiers.

A poorly maintained or improperly used portable humidifier can certainly put your health at risk. But there is also plenty of evidence that a properly maintained and operated humidifier can help keep you healthy, especially if you or others in your home suffer from allergies and asthma. Below is an overview of what you need to know.

Types of portable humidifiers

There are four basic types of portable humidifiers.

Steam humidifiers/vaporizers:In these devices, electricity heats water, creating steam that cools as it leaves the vaporizer. This is known as a “warm mist” system. Warm mist systems are not recommended for use around children because of the possibility of spilling hot water.

Evaporative humidifiers:These systems feature a fan that typically blows unheated water through a filter or other medium. This is known as “cool mist.” Like other cool mist systems, they are generally less costly than warm mist systems.

Impeller humidifiers:A high-speed rotating disk produces diffused droplets in a cool mist that is released into the room. Many impeller systems are significantly noisier than other designs.

Ultrasonic humidifiers:Ultrasonic systems use a rapidly vibrating ceramic diaphragm to produce a cool mist. While very quiet, some of these systems are known to generate and release white dust into the air.

Achieving the right humidity level

Humidifiers can help you add moisture to the air, but it is also important to monitor the humidity in your home in order to ensure ideal humidity levels. The best way to measure humidity is with a hygrometer, a simple device that looks similar to a thermometer but measures humidity. Hygrometers can be purchased at hardware and home-supply stores for less than $10.

The ideal humidity range is 30-50%. Humidity levels below 30% can cause dry, irritated skin, and can irritate the nasal passages. Increasing the humidity can make breathing easier for many people, especially for those with asthma or allergies or for someone with a cold.

On the other hand, humidity levels above 50% can result in water condensing on walls and other surfaces, encouraging the growth of allergens such as molds and dust mites. Humidifiers that are not properly cleaned and maintained can also disperse dangerous bacteria and other microorganisms into the air.

Tips for safely using a humidifier

The safe use of any humidifier depends on carefully following the instructions and guidelines provided by the manufacturer. Here are a few additional tips for safe operation of portable humidifiers:

1. Always use distilled water.Water straight out of the faucet contains minerals that will be deposited on your humidifier and can promote the growth of bacteria and other harmful microorganisms. Also, in some systems any expelled minerals will be deposited on furniture and other surfaces as a white dust.

2. Change the water every day.This is especially important for cool mist systems. On a daily basis, empty the tanks, thoroughly dry all surfaces, and refill with clean distilled water.

3. Clean the humidifier every three days.Always be sure to follow the manufacturer’s directions. The best safe cleaning solution is 3% hydrogen peroxide, commonly available in pharmacies and other stores. Although some manufacturers may recommend bleach or chemical disinfectants, be sure to use these according to directions.

4. Change any filters on a regular basis.Some humidifiers have filters to trap some particles and microorganisms. Change filters frequently to avoid the possibility of mold build-up.

Choosing the right portable humidifier based on your needs will give you a good start in maintaining a healthy level of humidity in your home. By always following the manufacturer’s directions and maintaining your humidifier according to the guidelines above, you will help ensure a healthy indoor climate year round.