"Millions of buyers of ultrasonic humidifiers who thought they had finally found a safe and effective way to add moisture to the home in the winter heating season have something new to worry about.
Scientists at the Environmental Protection Agency have discovered that the ultrasonic machines can fill household air with tiny particles of minerals and pieces of microorganisms that can be inhaled deep into the lungs, where they may cause allergies or illness.
The potential hazard of ultrasonic humidifiers may come as a bit of a shock to those who bought the machines in the last five years because they are whisper quiet, energy-efficient, effective moisturizers that, unlike cool-mist humidifiers, did not breed harmful microorganisms and spew them into the air.
The new finding explains a number of complaints from consumers who have reported that the use of an ultrasonic humidifier produced a chronic cough or allergic symptoms in one or more household members.
The problem is especially severe when consumers use ordinary mineral-laden tap water to fill their humidifiers and when the machines are not cleaned each day to keep bacteria and molds from accumulating. Particle levels in a closed bedroom could exceed the Federal standard for particles in outdoor air by nearly 50 times, the study showed."