A humidifier is a household appliance that increases humidity (moisture) in a single room or in the entire home. There are point-of-use humidifiers, which are commonly used to humidify a single room, and whole-house or furnace humidifiers, which connect to a home's HVAC system to provide humidity to the entire house.
The most common humidifier, an "evaporative" or "wick humidifier", consists of just a few basic parts: a reservoir, wick and fan.
The wick is a filter that absorbs water from the reservoir. Evaporation of water from the wick is dependent on relative humidity. A room with low humidity will have a higher evaporation rate compared to a room with high humidity. Therefore, this type of humidifier is self-regulating: As the humidity of the room increases, the water vapor output naturally decreases. These wicks regularly need cleaning and replacement—if this does not happen, the humidifier stops humidifying the area it is in and the water in the tank remains at the same level.
The fan is adjacent to the wick and blows air onto the wick, thus aiding in the evapiration of the water within.
Other types of humidifiers include:
- Vaporizer (Steam Humidifier) (Warm Mist Humidifier) — Boils water, releasing steam and moisture into the air. A medicated inhalant can also be added to the steam vapor to help reduce coughs. Vaporizers are more healthful than cool mist types of humidifiers because steam is sterile and free from minerals. Vaporizers use more electricity to boil the water.
- Impeller Humidifier (Cool Mist Humidifier) — A rotating disc flings water at a diffuser, which breaks the water into fine droplets that float into the air.
- Ultrasonic Humidifier — A metal diaphragm vibrating at an ultrasonic frequency creates water droplets that silently exit the humidifier in the form of a cool fog. Ultrasonic Humidifiers should be cleaned regularly to avoid bacterial contamination which may be projected into the air.
- hydro-pneumatic capillary system Humidifier (Non Electric Humidifier) A water powered technology that uses no electricity at all to power the unit. Advanced valve and capillary system.
For buildings with a forced-air furnace, a humidifier may be built right into the furnace. They can also protect wooden objects, antiques and other furnishings which may be sensitive to damage from overly dry air. In colder months, they may provide substantial energy savings, since as humidity increases, occupants feel warm at a lower temperature. These units are typically called bypass humidifiers (because they are connected between the heated and cold air return ducts, using the pressure difference between these ducts to cause some heated air to make a bypass through the humidifier and return to the furnace). The humidifier should usually be disabled during the summer months if air conditioning is used; air conditioners partially function by reducing indoor humidity. There are three basic styles:
- Drum style: A pipe brings water directly to a reservoir (a pan) attached to the furnace. The water level in the pan is controlled by a float valve, similar to a small toilet tank float. The wick is typically a foam pad mounted on a drum and attached to a small motor; hot air enters the drum at one end and is forced to leave through the sides of the drum. When the hygrostat calls for humidity, the motor is turned on causing the drum to rotate slowly through the pan of water and preventing the foam pad from drying out.
- Advantages include:
- Low cost
- Inexpensive maintenance (drum-style pads are cheap and readily available)
The use of a humidifier can allow the reproduction of dust mites or the growth of harmful mold, which can be especially harmful for children and the elderly. The relative humidity should be kept between 30% and 50%. . Can also cause Hypersensitivity pneumonitis (humidifier lung)
A controller that measures and controls relative humidity. A humidistat may be used to control either humidifying or dehumidifying equipment by the regulation of electric or pneumatic switches, valves, or dampers.
