If You See This Black Gunk in Your Humidifier, You Need to Clean It ASAP

If you have allergies, dry skin, asthma, or just prefer a more humid environment, you’ve probably got a humidifier at home. Humidifiers add moisture to the air to prevent dryness and require regular cleaning (at least every three days!) to run smoothly. But if you’re not diligent about its upkeep, you might end up seeing tons of black gooey substances built up in the reservoir or just underneath it — and that’s not a good thing. Below, experts explain what this black gooey substance is and how to get rid of it once and for all.

What Is the Black Gooey Substance in My Humidifier?

The black gooey substance in your humidifier is a miasma of things you probably don’t want in there. It’s a combination of biofilm, which is a slimy layer of bacteria, mold, and fungi; and mineral deposits, which usually come from hard water. There may even be some regular household contaminants in there, like dust, skin cells, and microscopic food particles.

“This gunk is essentially a biological soup fed by both water impurities and airborne contaminants,” says Glenn Gault, CEO at Gault Heating & Cooling. All of those things combined make the perfect nutrient-rich breeding ground for bacteria.

Why Does This Black Gunk Build Up?

The gunk builds up for a few reasons, the main one being that you’re not cleaning your humidifier regularly. That allows minerals from hard water to build up, as well as fosters microbial growth from water that’s just sitting there. If you use essential oils or straight tap water, these could be part of the problem as well.

Is the Black Gunk in My Humidifier Dangerous?

“Inhaling mold spores and bacteria isn’t good for health,” shares Brad Roberson, president of Aire Serv, an HVAC repair company. “It can cause respiratory issues, particularly for people with asthma, allergies, and weakened immune systems.” Plus, Gault says, the stuff in your humidifier impacts the machine’s performance — so you don’t get the same health benefits from it anyway if the buildup is in there.

The Best Way to Clean a Humidifier

Gault and Roberson both note that for the best way to clean your humidifier, you should follow the steps below. Roberson suggests wearing a face mask while you do it, especially since the black gunk can be toxic.

What You’ll Need:

• Distilled white vinegar or food-grade citric acid

• Warm water

• 3% Hydrogen peroxide

• Soft-bristle brush or toothbrush

• Microfiber cloth

• Face mask

How to Clean a Humidifier:

1. Turn off and unplug the humidifier, remove all detachable parts, and empty out the water tank.

2. Fill the tank halfway with warm water and add a cup of vinegar. If you’ve opted to use citric acid, add one or two tablespoons to the water instead of the vinegar. Swirl the contents around the water tank, being sure to coat all the surfaces. Let this sit for 20 to 30 minutes.

3. While the water tank is soaking, dip the brush into the solution and scrub all the other components.

4. Once the water tank is done soaking, rinse everything — the tank and all the parts you scrubbed — with warm water. Wipe all the surfaces with hydrogen peroxide and let it sit for 10 to 20 minutes to kill any lingering contaminants.

5. Rinse everything one more time, then dry with a microfiber cloth and reassemble. Be sure all the parts are completely dry before putting the humidifier back together.

How Can I Prevent Black Gunk Buildup in the Future?

The black gooey substance in your humidifier won’t come back as long as you follow a cleaning protocol. First, you’ll want to switch to distilled or demineralized water instead of tap water to mitigate the minerals in water that cause slime growth. Next, you’ll need to set up a schedule: Empty and rinse the tank every day, and do a deep clean of all the components every third day. Gault says you can also add a small amount of hydrogen peroxide to the tank, about a teaspoon per gallon of water, to keep mold and bacteria away. Any more peroxide than that, and it could damage the humidifier.

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