Humidifiers evaporate water to raise the relative humidity in a room. This is especially important in the winter, when the cold outdoor air lowers the humidity inside your home. Unfortunately, there may come a time when your humidifier stops working and the air becomes dry again. Whether it doesn't raise the humidity anymore or it won't turn on at all, there are several reasons why a humidifier won't work.

Lack of Power

See if there is power going to the humidifier. If the digital readout is blank, the motor isn't running and no other lights are on, there may not be adequate power. Check the power cable to make sure that it is still plugged into an outlet. If it's plugged in and still doesn't have power, check your circuit breaker to see if the humidifier tripped the breaker. Some higher-powered humidifiers trip circuits in homes with older wiring. If you're still not sure, connect a working appliance to the outlet, such as a lamp. If the lamp works, then you know there's a problem with the humidifier itself rather than the outlet. Bring it into an appliance repair shop to fix the problem.

Lack of Water

A humidifier adds humidity to a home's air by evaporating the water in its reservoir. If the humidity isn't rising with constant use of the humidifier, check the reservoir to see if it's empty. If it's empty, fill it with fresh tap water. Depending on the dryness of the air, the size of the reservoir and the type of humidifier, you may have to refill the reservoir several times each day. Make filling the humidifier a regular chore if you want to keep your home's air moist.

Low Humidity Settings

Check the settings on your humidifier. The settings allow you to choose the humidity threshold of the appliance. For instance, if you choose a humidity of 45 percent, the humidifier will turn off automatically once the relative humidity of the room hits this percentage. If your air is still dry once the threshold is hit, raise it using the settings buttons on your humidifier. Some humidifiers even give you the option of running the appliance all the time without a humidity threshold.

Old Filters

There may come a time when your humidifier is running, but the room's air stays dry. In this case, the problem may be the humidifier's filter. As a filter gets old, water doesn't pass through it as easily, hampering the abilities of the appliance. If your humidifier's water reservoir isn't emptying as fast as it used to, this is an indication of an old, dried-out filter. Consult the humidifier's manual to find out the exact type of filter you need. Purchase a new one and install it in the appliance to get your humidifier working properly again.