If you tend to get congested during the winter months or your skin gets brittle and dry, a humidifier can be a good thing to have. This is because your home's heating system can suck moisture out of the air as it runs. One of the leading brands of humidifiers is Aprilaire. Most people know that to run a basic humidifier you need to fill it with water and turn it on. However, Aprilaire humidifiers work with your furnace, so they can be a bit more complicated.
Set your humidifier to suit your home. Depending on its current humidity, you'll want it to moisturize either more or less than the default setting. To do this put the setting knob on 5 or "normal." Then wait a day or two. If your home gets too humid (for example, you see water on the windows) turn it down a notch. If your home feels too dry move it up a notch. Repeat this step as needed until your find your comfort zone.
Control your system manually. Once you've set your system up, it will automatically adjust the relative humidity whenever the furnace is in use. Each time the temperature outside increases one degree the humidifier will adjust your indoor humidity by half a percent. If you're not happy with this, change it. First, switch the knob to "off." Then turn it counter-clockwise until you hear a click. Then turn the dial to select your preferred humidity level, one through seven. This will be the new level for the current outside temperature.
Test your system periodically. Put the system in test mode by putting the knob on "test." Check that the furnace is turned on (there is usually a switch on the side of the appliance) and that the furnace blower is functioning properly. Then see if your thermostat is set to heat, meaning it's programmed to a temperature higher than the current indoor one. Once the furnace is set up correctly, the humidifier should run for 60 seconds in this mode. If it doesn't contact an heating, ventilating and air conditioning (HVAC) professional.