What is the difference between a cool passover humidifier and a heated humidifier?
Humidifiers function through the process of water evaporation as air is drawn across a pool of water. A cool passover humidifier tries to use the surface area of the water to maximize humidification. Therefore, these units are usually wide and flat, and are usually stand-alone units. Since they do not use electricity to heat the water, they can be beneficial if the power source is limited, such as when using 12V. Heated humidifiers increase the evaporation rate by heating the body of water. The evaporative process is enhanced due to the higher temperature of the water. Since the surface area of the water is not as important, heated humidifiers can usually be much more compact than passover humidifiers. However, they do take a substantial amount of electricity to heat the water, and thus cannot usually be used with a 12V power input.
