Furnace humidifiers are the best way to control the relative humidity of all the air in a house. They are installed as part of the ventilation ductwork near a furnace, and provide humidity whenever a furnace is running. Generally speaking, furnace humidifiers are fitted when a heating system is installed, since they are designed to be fully integrated into it.
All furnace humidifiers apply the same basic principles to humidify hot air, but they come in two basic types. The first type is a flow-through design, where water flows into a humidifier and then drains out. These are commonly mounted on the air return duct on the furnace and connected to its hot air supply. Inside the humidifier, warm air absorbs moisture from an evaporator pad, and from there goes into the furnace to be dispersed throughout the house.
Furnace humidifiers also come in a second variety, namely the reservoir humidifier. In this type, there is a reservoir of water and a rotating drum to introduce moisture into the air. One risk associated with these humidifiers is that in some cases, bacteria and mold can grow in the reservoir’s standing water. Microorganisms like these can lead to humidifier fever, an inflammation of the lungs. However, proper care and cleaning of the reservoir can reduce or eliminate this risk.
Airborne pollutants were a common problem associated with earlier designs of furnace humidifiers which used an evaporative wick. In these types, a sponge was used to soak up water which was then passed into the air. Not unlike the way a dish sponge can grow mildew over time if not kept dry, these sponges easily became breeding grounds for such organisms. Frequent cleaning or replacement of the sponges was the only way to avoid contamination of the air inside a home.
Thankfully, today’s designs are much safer and require less maintenance. Another convenient feature that comes with some newer furnace humidifiers is a humidistat. In the same sense that a thermostat regulates temperature, a humidistat regulates the relative humidity of a home. These units measure the moisture content of the air coming into the humidifier and adjust its function accordingly.
While furnace humidifiers are convenient, some prefer tabletop humidifiers that serve only a single room. These do have advantages over whole-house humidifiers since they are uncomplicated and do not need to be installed by a professional. The smaller, more portable humidifier may be the preferred alternative if only one room needs extra humidity.