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6 Places Mold Can Hide in Your Home — and How to Get Rid of It

Mold can cause health issues ranging from mild to dangerous. Here’s what to know

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Robert Samuel Hanson

Outdoor mold plays a crucial role in nature by breaking down dead organic matter. But indoors, it can be a nuisance or even a danger to your health.

How worried should you be? That depends, says forensic scientist and certified mold inspector Joshua Leviton; the answer is complex since mold can affect each person differently.

Here are unexpected places in your house where mold might be hanging out, how dangerous it is to your health and what to do to get rid of it for good. 

Hiding in the walls … or behind the wallpaper

Sound like something out of a horror movie? It kind of is. Mold remediator Tal Saar says growth in drywall is a huge issue.

“Ninety percent of the jobs that we do involve drywall,” says Saar, the founder of a New York-based mold remediation company. “That’s where the majority of the issue is because it’s porous. So once you have water damage with the drywall and the porous material, you’re going to get mold and it’s going to come by fast … within 24 to 48 hours, you can have a mold issue.”

According to Saar, water damage in drywall can lead to the growth of black mold. Even though you might not see mold growth when you have water damage, it’s crucial to address the problem quickly.

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You’ll likely notice the water damage right away, Saar says. Unfortunately, there’s only one way to effectively address the issue — remove the drywall and fix whatever caused the damage. If you don’t address the source of the problem, the mold will just come back.

Mold can also grow behind wallpaper, Leviton says. An easy-to-spot sign is if the paper starts to peel, though that does not necessarily mean you have a mold problem, he adds. It might just be humidity messing with the glue.

Lurking inside HVAC systems

Heating, ventilation and air-conditioning systems, or HVAC for short, are another area of the home where mold can live.

You may suspect or know there’s mold in your HVAC system if you or a professional has identified a moisture problem in your home, you see mold near the intake to the system, you smell a musty odor coming from the system or a routine check led to the discovery of mold.

The U.S. Environmental Protection Agency (EPA) says, “Many sections of your heating and cooling system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists.” Be aware that not everything that looks like mold is mold. Only experts can determine that, and a laboratory analysis may be required for final confirmation. “For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it,” the EPA states.

The EPA says HVAC systems, along with drain or condensate pans, need to be “checked routinely” to prevent and address any mold growth. Filters for the HVAC system need to be “kept dry and changed frequently,” and equipment should be evaluated by a professional HVAC contractor if it is more than 10 years old or failing to keep your house comfortable.

According to Leviton, mold can grow in the vents or ducts, as well as on the HVAC coil, which, in his experience, is usually where a more dangerous type of mold grows.

If you suspect or see mold growth on or in the HVAC system, Leviton says it’s time for testing. The EPA advises that you refrain from running your HVAC system and consult its guide — “Should You Have the Air Ducts in Your Home Cleaned?” — before moving forward.

“My recommendation would be to first get it tested to find out what species are present, which will then determine whether you need an HVAC company or mold remediation company to do the removal,” Leviton says.

Growing on clothing

Another out-of-sight spot for mold to grow is on the clothes in your closet — particularly if you have a tightly packed closet with poor air circulation.

Mold grows best in closets when humidity levels rise above 70 percent, Leviton says, and natural materials, including wool and cotton, are more prone than others.

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Should you just throw moldy clothes in the wash? Leviton says his cleaning recommendations for household items harboring mold can vary greatly since some people are very sensitive to mold and others are not. If he was dealing with a slightly moldy piece of clothing, Leviton says, he would “put it in a washing machine with some vinegar” to see if that got rid of visible mold. Saar, on the other hand, recommends taking slightly moldy clothing to a dry cleaner.

Note that simply trying to clean moldy clothing is “totally not enough” for people who are highly sensitive to mold, Leviton says. They might consider just throwing the clothes away.

To get rid of airborne mold spores after you remove the clothing, Leviton suggests running a high-efficiency particulate air (HEPA) filter — especially since anytime you handle something with mold on it, you’re effectively “disturbing it” and sending spores into the air.

The Centers for Disease Control and Prevention says humidity should not go over 50 percent. A dehumidifier might help keep mold at bay and allow the air in your home to flow freely, the CDC says.

Living on the backs of furniture

Mold on furniture can be exceptionally tricky to spot when it occurs on the backside of an item.

“For furniture, it tends to be on that particle-board backing on like Ikea furniture,” Leviton says. “So that’ll be like side tables or behind headboards a lot of times.”

Because that type of material is porous, it can be very hard to effectively clean — you don’t have the option of submerging it in a cleaning solution or throwing it in the washing machine.

“When it comes to the backing of furniture, usually I would replace [the furniture] if possible,” Leviton says. “Usually, you can clean it, but the mold will stay in the porous material.”

The mold monster under your bed

You might have checked for monsters under the bed as a kid; now it might be time to check for mold.

Leviton says keeping your mattress on the floor puts your bed at the highest risk of mold growth: “If condensation does happen, then it’s kind of got this nice little petri dish that’s been created by the floor and the mattress. So it’s better to have it off the floor so that air can circulate.”

And frankly, Leviton says, if you do find mold, it’s probably time for a new mattress. He says you could try to clean it but that would be extremely cumbersome and pretty much impossible to completely rid it of mold.

“I don’t know how you would get all of the mold because it would grow inward, and you can’t really get deep enough, I don’t think, with cleaning unless you were able to submerge it in something like vinegar,” he says. “But I don’t know if there’s a way to because it’s such a large object.”

If your mattress is raised off the ground and mold-free, it is still possible for mold to grow under your bed.

“I’ve seen it on the wooden slats under the mattresses before because if the bed is up against the wooden slat, then it creates kind of like a little mini-environment where moisture can just kind of sit,” Leviton says.

If you find mold growing on the slats, Leviton says cleaning them could be effective if the wood is sealed. If it’s not, he says to replace them since the mold has likely “grown into the pores,” which makes them impossible to fully clean.

He adds there are products on the market such as encapsulating paint meant to trap the mold into the wood, but they are not guaranteed to work.

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Spinning in your washing machine

It’s ironic that a costly home appliance meant to make things clean … can be kind of icky. Mold can grow in your washing machine — particularly on the rubber gasket that prevents water from flowing out of the washer when in use. And that means it can get on your clothes.

“[The gasket] can be replaced, but it’s weirdly expensive,” Leviton says. “But it’s very hard to clean it out … it’ll start to discolor and turn black, and it’s not usually anything beyond Cladosporium,” a common indoor mold.

Energy Star, a program run by the EPA, says to follow your washing machine’s manufacturer’s maintenance instructions if you’re trying to rid it of mold.

“Some manufacturers recommend rinsing the washer each month by running a normal cycle with 1 cup of bleach and wiping down the compartments to help reduce the risk of mold or mildew buildup,” the website reads. “Consult the product owner’s manual and review other recommendations for regular maintenance.”

To prevent mold growth, Leviton wholeheartedly recommends leaving the washing machine door open after use for a while, “so then the moisture can evaporate.”

Where there is water, there can be mold.

Who is more likely to be affected by mold?

People with preexisting conditions might react more strongly to mold, including those who are sick or have respiratory issues, allergies or asthma, according to the American Industrial Hygiene Association website. Infants and children, older people and those who are pregnant also could have more adverse reactions.

Leviton says some of his clients have exhibited brain fog — though research on this symptom is limited.  

You can get tested for mold allergies. But it’s important for everyone to try to avoid mold growth in their homes because even less sensitive people can react to mold — anything from an increased risk of allergic and upper-respiratory disease to bothersome symptoms such as coughing and wheezing, according to the CDC.

Which molds are the most dangerous?

Again, that depends, Leviton says. Just like people react differently to molds, they react differently to different kinds of molds. One type of mold can be relatively benign to one person and seriously harmful to another.

The most common types of mold you might find in your home, according to the CDC, are Cladosporium, penicillium and aspergillus. Stachybotrys chartarum — referred to as black mold — can be found in the home, but it is less common.

Can you clean mold yourself?

Leviton says that’s not the best idea. The first thing you need to know before you clean mold is the type you’re dealing with. You can hire a professional to test the mold, or you can purchase an at-home test.

Leviton says to be wary of doing it yourself since that often ends up costing the same as hiring a professional after sending samples to a lab and potentially needing a professional to interpret the results anyway. If you hire a professional, they should be able to tell you what steps need to be taken to address the mold issue effectively.

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