Cleaning and disinfecting your humidifier helps ensure you won't encounter harmful effects from bacteria buildup. The U.S. Consumer Product Safety Commission (CPSC) has found that bacteria and fungi released into the air with humidifier mist not only increase allergy and asthma sufferers' discomfort, but can cause flu-like symptoms or serious infections for anyone.
Spot warning signs of an unhealthy humidifier
Visible film or scum on the sides or bottom of the tank, on exposed motor parts or on the surface of the water can indicate a problem. Risk increases if the tank is already home to crusty buildup known as scale. Scale, composed of minerals found in tap water, isn't the problem, but it does create a hospitable environment for bacteria to thrive.
The cool-mist cleaning challenge
With cool-mist humidifiers, it's important to practice proper cleaning and disinfecting on a regular basis. Since the water isn't brought to a bacteria-killing boil, cool mist humidifiers can cause big problems if water is left sitting between uses. Microorganisms like bacteria and mold collect and multiply in the standing water and are sent out into the air when the unit is restarted.
Some people are concerned when using cool-mist humidifiers because of tiny, dust-like mineral particles that settle on nearby surfaces. Certain models discharge high amounts of this white dust when filled with tap water. It isn't clear if there are any health effects from inhaling the mineral dust; it may all depend on the types and amounts of minerals present. The number of particles released can be greatly reduced if distillation water purifiers are used and somewhat reduced if the water has been put through deionization or reverse osmosis. Some humidifiers now come with UV light purifiers to fight bacteria and viruses.
How to avoid problems
Keeping a humidifier out of the bedroom and in a central location can help avoid health effects but should only serve as a backup to regular disinfecting. Most models come with detailed cleaning instructions, and many have dishwasher-safe reservoirs for easy cleaning. As a rule, water should be emptied after every use and the tank cleaned every few days.
Filters and things
New humidifiers often include features to help users control bacteria - antibacterial filters, ionic silver sticks, UV light, bacteriostatic chemicals and the like. Demineralization cartridges can be purchased to solve the problem of white dust (if buying distilled water isn't practical), but more studies need to be done on their effectiveness. A good rule is: if you see particles, the cartridge probably isn't working. If there aren't already humidity controls or a humidistat on the unit, a digital hygrometer can be purchased separately to measure moisture levels and prevent mold growth.