Black mold in a dehumidifier

Why it grows there

A dehumidifier is built to hold what it pulls from the air. The federal definition lists it among the four parts: a means for collecting or disposing of the condensate. In most units, that means a bucket.

Mold needs moisture. The EPA’s rule of thumb: dry a wet area within 24 to 48 hours, and in most cases mold will not grow. A bucket left full for days misses that window, and so can a damp coil in a unit that stays off for weeks.

Dark spots don’t tell you the species, and you don’t need to know it to clean them. The EPA’s cleanup advice doesn’t change by color.

Cleaning what you can reach

For hard surfaces, the EPA’s advice is short: scrub mold off with detergent and water, and dry completely.

1. Unplug, then take out the bucketWork on the unit only when it’s off the outlet.
2. Protect yourselfWear gloves. The EPA recommends long ones, to the middle of the forearm. To avoid breathing spores, it suggests an N-95 respirator.
3. Scrub, rinse, dryThe bucket and its lid first. Let every part dry before you put it back.
4. Check the filterIf your unit has one, clean or replace it the way the manual says.

A dehumidifier is well under that size.

What you can’t reach

The coils and the fan sit behind panels, near wiring. Don’t pour water into the unit.

Check the model number against CPSC recalls while you’re at it. Most dehumidifier recalls name a fire hazard, not mold, but the label you need is the same.

Don’t let water stand

The EPA gives the same advice for air conditioners: keep drip pans clean and drain lines unobstructed and flowing properly. It fits a dehumidifier too.

• Empty the bucket often while it runs, and let it dry before storage.
• Use a hose to a floor drain or sump if you have one, as ENERGY STAR® describes, so the condensate leaves as it forms.
• No drain lower than the unit? A built-in pump pushes it up and out. The drain planner tells you which setup fits.

Mold in the room as well

A dehumidifier lowers humidity, but it doesn’t remove mold that’s already on walls. The EPA’s target indoors is below 60%, ideally 30 to 50%. If the room stays above that, check the size of the unit against the room.

Then find the water. The EPA puts it in one line:

Clean up the mold and fix the leak, or it will most likely come back. When growth covers more than 10 square feet, the EPA points to its guide for schools and commercial buildings. If you hire a contractor, it says to pick one with mold cleanup experience.

Sources

Every figure and quote on this page comes from these, each with the date we read it.