Power Humidifiers

Bypass flow-through power humidifier

Bypass flow-through style (bypass) - uses a pipe to bring water directly to an electrically controlled valve at the top of the humidifier. Air passes through an aluminum “biscuit” (often called a pad or water panel; the term "biscuit" emphasizes the solid rather than foamy form) which is similar to a piece of extremely coarse steel wool. The biscuit has a coating of a matte ceramic, resulting in an extremely large surface area within a small space. When the humidistat calls for humidity, the valve is opened and causes a spray of water onto the biscuit. Hot air is passed through the biscuit, causing the water to evaporate from the pad and be carried into the building.

Advantages include

Reduced maintenance (new biscuit is needed only when clogged with dust or mineral deposits, typically once per year)
Lack of a pan of potentially stagnant water to serve as a breeding ground for mold as with a drum-style humidifier
No incidental humidification caused by a constantly replenished pan of water in a high velocity air stream
Reduced requirement for expensive air filters
Uses little electricity