The United States Environmental Protection Agency says that the way to control indoor mold growth is to control moisture. Thats just one reason to invest in a portable dehumidifier. If you want to protect your walls, building foundations, furniture, electronics or even the strings on your piano, a portable dehumidifier can be just what you need.

Portable dehumidifiers work on the same physical principles as those of full-size units: cold air holds less water than warm air. All dehumidifiers draw in humid air from the room, cool the air so that the water falls into a reservoir bucket, warms the dried air back up to room temperature, and releases the dried air back out into the room.

The size of the fan, along with the power of the fan motor, determines how large a room your unit can dehumidify. Most dehumidifiers use blade-type fans, but some of the larger units boast the more efficient, squirrel cage-type fans, similar to those used in furnaces.

The advantages to portable units over full-size models are numerous. First and foremost, portables use less energy sometimes as little as half the energy of a full-size unit. This will save you a bundle on your next electric bill. Second, they are easier to move. Most people can pick up a 29-pound portable unit and move it from room to room, depending on where you need it most.

Best of all, portable dehumidifiers are almost as thorough as larger units. The square footage of air dehumidification, as well as the size of the reservoir, average as high as some of the mid-range full-size machines.

One downside to portables is that, because the components are packed more tightly, the compressor will tend to frost up and spread to other components. As a result, some manufacturers have included a frost warning light. When it goes off, you will know that the compressor needs to be defrosted.