Many people use portable cool-mist humidifiers to increase moisture levels in the air inside their homes. When used as directed by the manufacturer, portable cool-mist humidifiers are a safe product. However, using one without properly cleaning and disinfecting it on a regular basis could contribute to additional breathing problems for people who have asthma, severe allergies and other respiratory difficulties.

There are three types of portable humidifiers. Vaporizers contain a heating element that boils water. They put moisture into the air by sending out a stream of hot mist. Ultrasonic humidifiers produce a micro-fine mist when water is passed over an ultrasonic nebuliser (high frequency vibrating apparatus). Cool-mist humidifiers work without heating the water. A motor forces the water droplets into a mist which is then dispersed into the air.

Potential Health Risks of Portable Humidifiers

Portable humidifiers are not likely to cause health problems if users follow the manufacturer's directions. This usually means emptying left-over water after each use, as well as cleaning and disinfecting the water reservoir on a regular basis.

However, of the three types of portable humidifiers, the cool-mist humidifier may contribute to health effects if water is left sitting from one use to the next because:

• Bacteria can collect and multiply in sitting water
• A cool-mist humidifier does not boil the water, so it does not kill the bacteria
• Re-starting the cool-mist humidifier could send spores of bacteria into the air in your home

The bacteria spores could then make matters worse for people who already have difficulty with their breathing.

Many consumers have concerns after using cool-mist humidifiers because they notice tiny, dust-like particles on furniture nearby. Some models may release high concentrations of the particles into the air when they are filled with tap water.

These particles are made of the same materials that cause the build-up of scale inside kettles, and are considered harmless to most people. However, if the tap water used in the cool-mist humidifier contains toxic substances, there is a risk that the particles could be harmful.

The number of particles released into the air is generally much lower when distilled water is used.

Using Your Cool-Mist Humidifier Safely

To safeguard your health when using a cool-mist humidifier, you should:

• Clean and disinfect your water reservoir of your humidifier on a regular basis according to the manufacturer's directions. Instructions may vary depending on the type of humidifier and frequency of use.
• Never leave water sitting in a cool-mist humidifier when you are not using it.
• Always empty the water reservoir when you turn off the humidifier.
• Clean and refill only when it is to be used.
• Keep the humidifier in a central location and out of your bedroom - especially during the night.

Another option is to use distilled water. However, in most cases tap water is fine, as long as you change the water and clean your humidifier on a regular basis.

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