What people should be aware of when using a humidifier

Humidifiers are designed to help you breathe better, but depending on the type you have and the water you use, it might also be affecting your air quality at home.

"It's not that I am saying humidifiers (are) completely bad for people. It's just we should be aware that the water quality we put into the humidifier is directly reflecting the quality of the indoor air you're breathing," said Ran Zhao, an assistant professor of Environment Chemistry at University of Alberta.

Zhao studies indoor air quality and he has published research showing using tap water in a cool-mist or ultrasonic humidifier can send high concentrations of particulate matter into the air.

"Those little particles can go all the way into the deeper sites of your lungs and with (that) they can carry whatever chemical they're associated with."

He has found levels in a home consistently using a humidifier are comparable to a polluted city.

"From the mass point of view, it's equivalent to a polluted city. But from the chemical composition point of view, we're not talking about emissions coming from industry, cars and other human sources of air pollution."

According to Health Canada, "the number of particles released into the air is generally much lower when using distilled water. However, tap water is fine in most cases, as long as you change the water and clean your humidifier on a regular basis."

Zhao's advice is to do your best to find the cleanest water you can afford or find a humidifier that uses evaporation to generate the mist.

He notes more research is needed to look into the potential health hazards, “to prove that it is indeed harmless or, alternatively, maybe there is some potential health hazard or health concern if we continue inhaling such a high concentration of particulate matter, even though the chemical itself is not harmful.”

Health Canada also said cool-mist humidifiers don't boil the water and that a health risk can develop if the water is left sitting, as bacteria can collect and multiply.