According to this report
"Humidification should preferably use evaporative or steam humidifiers, as cool mist humidifiers can disseminate aerosols contaminated with allergens"
Similarly, a NY Times article published in 1988 states that:
"Anyone who is allergic to molds should not use cool-mist vaporizers or ultrasonic humidifiers, since both spray water into the air, Dr. Burge said. Cool-mist vaporizers pose a greater hazard since they can disperse live organisms into the air. Studies have linked the use of cool-mist vaporizers in hospital rooms with severe respiratory infections."
I understand this to mean that humidifiers increase risk of infection because they spur mold, allergens and other "live organisms" into the air - thereby increasing the amount of allergens and "toxic" substances we inhale.
1) Is there any well researched evidence to back up the claim that humidifiers spur "mold", "allergens" and "live organisms" into the air and increase respiratory infections?
2) The NY Times article states that studies have linked humidifiers to serious infections "in hospitals". Does this apply to healthy individuals as well?
3) Finally, are all humidifiers created equal in this regard?
For those of you who are unaware there are several types of humidifiers:
Steam vaporizers - uses electricity to generate steam
Ultrasonic humidifiers - oscillates 1.7 million times a second to break water into a fine mist
Evaporators - produces humidity by blowing air past evaporating water