A humidifier is a device used to maintain a specified humidity in a conditioned space. The use of a humidifier in cold weather can lead to savings in energy because humid air feels warmer than dry air at the same temperature. Turning on a humidifier when it's cold outside will increase the heat index of an interior space and make 20°C (68°F) feel like 24°C (76°F), as a result of which thermostats can be set lower. Portable units should be placed in frequently used areas such as a living room or bedrooms. Whole-house humidifiers are also available.

 

In addition to cutting energy bills, humidifiers also help alleviate the problems caused by dry air including itchy skin, scratchy throats, static electricity, and damage to furnishings and woodwork.

 

The relative humidity in a home should ideally be in the range 20 to 40 percent. Over-humidifying can lead to condensation on windows and dampness on walls.

 

Compare with dehumidifier.