Do Furnace Humidifiers Cause Mold?

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You probably know that a leaking pipe or an overly humid bathroom can be a source of mold growth. If you have a humidifier attached to your furnace, mold could have another opening to enter your home. With proper maintenance, you can reduce your risk of dealing with problem mold in your home.


How Furnace Humidifiers Work

In cold weather, your furnace supplies your home with hot air, keeping you and your family comfortable. The air in the wintertime is drier than at other times of the year; the heated air supplied by the furnace is also very dry. Furnace humidifiers add moisture to the air. This can ease problems with dry skin and nosebleeds. Furnace humidifiers contain a reservoir of water. The water is either dripped through an evaporative pad or picked up by a rotating drum. The warm air from the furnace blows over the pad or drum, picking up moisture and bringing it into your home.


Mold Issues

Because the interior of a furnace humidifier is a moist environment, it is at risk for mold growth. Mold can grow on the absorbent padding inside the humidifier or on the interior walls. If mold growth goes unchecked, the furnace can blow mold spores into your home. This causes a foul, musty smell to come from your heat vents. The mold spores might land and start growing, leading to mold growth in other parts of your home.


You can remove mold from a furnace humidifier and prevent it from spreading into your home. Create a cleaning solution by combining equal parts water and white vinegar. Using a sponge, wipe down the interior of the humidifier and remove all visible mold, then wipe down the interior again. Next, fill a container with a mixture of one part water to two parts vinegar and soak the evaporative pad from the humidifier in it for 20 minutes. Rinse the pad with water, and then replace it inside the humidifier.



You might consider not using a furnace humidifier in order to reduce your risk of mold growing in your home. Reconsider, especially if you have wood floors or wooden furniture. Dry air does not just make people uncomfortable — it can also cause wood to shrink and warp. This can damage your furniture and make your floors uneven. If you want to continue using the furnace humidifier, make it part of your regular maintenance routine. Check it every month for signs of mold growth. Clean the interior and the evaporative pad with vinegar to prevent mold from growing there.