We seldom really think about air humidifiers, but we’d be disappointed and uncomfortable if we didn’t have them. As implied by their name, humidifiers increase the amount of moisture, either in the entire building or in just one room. They come in a number of different varieties, but the two most common are point of use humidifiers, which make it more humid in just one room, and furnace/whole house humidifiers, which are connected to the HVAC system in your home, providing the correct level of humidity to the whole building.

The most common way a humidifier works is by evaporation. These wick humidifiers use a wick, a reservoir and a fan. The reservoir is a tank of water that’s filled before turning on the humidifier, which provides the moisture that goes into the air. Other kinds of humidifier may not use a reservoir, substituting a dedicated water line instead for continuous feed. The wick is a filter which absorbs water. Evaporation of water from this wick is dependent on the humidity already in the air.

A room with low humidity often has a higher evaporation rate than one that has a high humidity. This makes this sort of humidifier self regulating, since the output of water vapor decreases as the humidity of the room goes up. However, these types of humidifier routinely need to have the wick cleaned and replaced. If the wick is allowed to remain dirty, the humidifier stops putting waver vapor into the room, and the amount of water in the tank stays at the same level. The fan is usually positioned near the wick, so that it can blow air on to it. This helps evaporation happen more quickly.

There are other humidifiers on the market. There are vaporizers, also known as warm mist humidifiers, and steam humidifiers. That releases moisture and steam into the air. It’s possible to add medicine to the vapor that sick people will inhale. This can reduce coughing. This type of humidifier uses more electricity, but may be healthier to be around since their steam is mineral free and sterile. Impeller humidifiers use a rotating disc, which flings water at a device called a diffuser. This diffuser breaks the water up into tiny droplets that enter the air. Ultrasonic humidifiers are also available. They use a metal diaphragm which vibrates at an ultrasonic frequency. It creates a silent fog that adds moisture to the air. It’s important to clean these humidifiers regularly to avoid bacterial contamination.

Forced air humidifiers are often built into the furnace of a building. They can help protect furnishings that are sensitive to damage from extremely dry air, and can help save energy. That’s because higher humidity makes it feel warmer in a building. It’s important to be careful when using this kind of humidifier if you suffer from allergies – if not properly maintained, it can allow dust mites and mold to reproduce. However, technologies are available in some models to reduce or prevent growth of these organisms inside the humidifier. Humidifiers are often also accompanied by a humidistat – a controller that can measure and control the humidity in the room, as well as the operation of the humidifier.