The Complete Handbook of Hand Dryers

Chapter 1: Understanding Hand Dryers

A hand dryer is a fixed electric appliance that removes water from skin by accelerating evaporation or by physically stripping water droplets with a high-speed air stream. That simple description hides the engineering compromises that determine whether a unit is an asset to a restroom or a maintenance liability. In this chapter, we will look at what a hand dryer is, how the main internal components work, and why those details matter for your electricity bill, your users' satisfaction, and your maintenance schedule.

Every hand dryer on the market performs the same fundamental task, but the way it performs that task varies enormously. The oldest and most common design is the warm-air dryer, which uses a resistive heating element to raise the temperature of the air passing over your hands. Warm air can hold more moisture than cold air, so raising the temperature increases the rate of evaporation. A typical warm-air dryer pulls in room air through a vent, passes it over a heating coil that draws anywhere from 800 to 2400 watts, and blows the heated air out at low velocity, usually under 5 meters per second. Drying time on these units is typically 30 to 45 seconds, which is fine for a low-traffic office restroom but painfully slow when a line forms behind a sink.

The other main design is the high-speed jet dryer, which relies less on heat and more on kinetic energy. A jet dryer uses a small, high-RPM motor to