No matter what type of humidifier is installed on your furnace, all must be cleaned at least once a year. Since humidifiers use water to create humidity, bacteria, mold and mildew can build up in the system without regular service. This means that these toxins can make their way through your system and into the air you breathe.
First, find out what type of humidifier you have. Your approach to cleaning and servicing the unit will change slightly depending on what kind you own.
A drum-style humidifier uses a rotating drum covered with an absorbent pad. As the drum rotates, it picks up water from a reservoir. Water evaporates as air is blown through the pad, creating a higher humidity level.
If you have this type of humidifier, the pad must be cleaned at least once a month and replaced at least once a year. To do this, turn off your furnace and locate the humidifier. It is at the warm air or return air duct of the furnace. Remove the humidifier cover. This will be held in place by either clips or screws. Find the rotating drum and determine if the pad is hard. If this is the case, the pad needs to be replaced. To remove the pad from the drum, take the clip off the drum spindle. If the pad is not hard, just clean it with a mixture of water and vinegar. Wring out the pad and attach it back to the drum.
While you have the humidifier open, make sure the water level is appropriate to the manufacturer's guidelines. Check to make sure that when the drum rotates, it is hitting the water in the pan.
A drip-style humidifier also uses an absorbent pad, but water is dripped on to the pad and air blows through it. These types of humidifiers often require less maintenance and have less chances of mold and bacteria buildup. This is because water flows down the pad and into a drain. There is no sitting water. Like the drum-style unit, these units should also be cleaned once a month. The pad should be replaced once a year.
To clean this humidifier, first turn off the unit and the water supply. Take the front panel off the humidifier and remove the frame with the absorbent pad. Take the pad off the frame and remove any mineral deposits. Use a utensil such as a putty knife to take off any deposits. If there is damage to the pad, either from use or from removing the deposits, replace the pad.
Reassemble the humidifier and restore the power and water.