* Droplet Size: Steam-size droplets. One micron droplets allow for immediate evaporation like steam. Competitive spray nozzle systems create up to 20 micron droplets, risking wetness on equipment and in ductwork.

* Health: All dissolved liquids are removed from the water feeding into ultrasonics. Steam systems emit dirt from the water up into the airstream, as confirmed by literature from steam manufacturers.

* Energy Cost: Ultrasonics generate 1 micron size droplets for as little as 1/13 the price of steam. This can save thousands of dollars in annual operating costs. In addition, ultrasonics turn on and off instantly, while steam units preheat, using more electricity.

* Maintenance: Since water is purified before entry into the ultrasonic humidifier, there is considerably less maintenance required of an ultrasonic system as opposed to steam.

* RH Accuracy: Ultrasonics provide instant on/off of mist. As soon as the air strays from the relative humidity set point, an ultrasonic humidifier instantly turns on. Steam canisters have flush cycles that may shut down the humidifier for up to 15 minutes or more. Heating elements inside those systems take time to reboil water to create humidity.