It's not the heat, it's the humidity; it's not the cold, it's the dryness.

In many parts of the United States, comfort means putting water into the air, taking it out, or both. That's where a humidifier comes in handy. It puts moisture into the household air to increase comfort--unless it quits working. Here's what to do if it quits.

How Does It Work?

A humidifier is an appliance designed on the principle of evaporation to increase moisture in the air. Water from a reservoir is added to an evaporation pad. A fan blows air through the pad. Fine droplets of water are placed in the air, thus increasing the humidity of the room. Both room and tabletop humidifiers work on this principle.

The two types of evaporative room humidifiers are drum and pump. A drum humidifier gathers water into an evaporation pad by immersing the pad, wrapped around a drum, into a reservoir of water. Water dripping from the rotating pad is absorbed by air current produced by a fan. A pump humidifier uses a pump to gather water from the reservoir and distribute it through the evaporation pad. Air from the fan blows through the pad and picks up the droplets to moisturize the air. Both types of humidifiers have operational controls, an evaporation pad, a fan, a water reservoir, and a humidistat. Some Forced-Air Distribution systems include an evaporative humidifier that works in the same way.

An ultrasonic humidifier works on completely different principles from standard room humidifiers. It's electronic. Beyond normal cleaning and testing of the electrical cord or switch, service of an ultrasonic humidifier should be left to a service technician.

What Can Go Wrong?

As you see, evaporative humidifiers are relatively simple appliances. Many humidifier problems result from dirty or damaged evaporative foam or filters. The electrical cord may malfunction. The humidistat, float control, and fan can be faulty.

The humidistat is sensitive to the level of moisture in the air. If humidity is lower than the control point set, the humidistat turns on the fan and pump (or pad rotator). See below for service instructions.

Many humidifiers have a hollow float inside that helps control water level, or tells the operator (that's you) when to refill the reservoir. In some cases, you'll need to adjust or replace the float (see below).

Fix-It Tip

Humidifier water conditioners are available that can soften the water and reduce algae to make your unit last longer. Stay away from those with perfumes that can leave residue to clog the evaporator pad. Clean the unit with a disinfectant at least once a season.