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If you have allergies or a chronic lung disease like asthma, you’re probably very aware of the effect mold can have on your health. But even if you have a healthy immune system and no allergies, mold can cause a variety of health problems — coughing, wheezing, and throat, skin, and eye irritation, to name a few. Mold is everywhere and, though you can’t fully control your exposure to it outdoors or in public spaces, you can check for mold in common places around your home and take measures to prevent and remove it.

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Read more about a new technology that can destroy mold.

What is mold and what causes mold in your home?

Mold is, by broad definition, a type of fungus that sprouts from microscopic spores floating in the air. When clusters of mold spores grow on surfaces, they start to reproduce and become visible to the human eye. If you have mold allergies, asthma, or another lung condition, even breathing in the microscopic pores can trigger an attack. If you don’t, you may not even be aware that there is mold in your home until you see it or smell it (a damp, musty odor is a good indicator that mold is growing nearby).

All homes have the key ingredients needed for mold growth: the presence of mold spores, a surface for it to grow on, oxygen, warmth, and darkness. When you add moisture, whether from a water leak, stagnant water, or high levels of humidity, into the mix, that’s where mold problems begin. Knowing where mold is commonly found in homes can help you prevent and treat it so you can keep your home and body healthy.

Common Types of Mold in Houses

Every patch of mold you see is actually an ecosystem of many different species and organisms. But there are a few specific types of mold that are more common than others. Let’s take a look at the four most common genera of mold that are found indoors. Within each of these genera are hundreds of species of mold, some of which are unhealthy and some benign.

Keep in mind that many types of mold produce a black pigment that protects them from sunlight, so there is no single species that is “black mold.” But mold colonies that are black in color are still very likely to harbor one or species that put toxin-laden spores and mold fragments into your air.


These molds interact with humans in many beneficial ways. At least 80% of the Vitamin C used in supplements comes from Aspergillus species, and others are used to make foods like the Japanese rice wine sake. However, many species produce asthma and allergy triggers along with carcinogenic toxins like aflatoxin. Aspergillus is also known to infect immunocompromised humans.


These molds perform a lot of decay in the natural world. Combined with their tendency to produce high levels of toxins, Alternaria species are some of the most prolific ruiners of crops. Their toxins are poorly understood, but they produce asthma and allergy triggers and can infect our mucous membranes.


These molds are extremely common around the world, and can grow in many environments and climates. While they produce asthma and allergy triggers, Cladosporium species do not produce any known toxins. However they are known for terrible odors.


This group of molds is best-known for their ability to produce the bacteria-killing substance penicillin, which has been used to help humans fight infections for decades. Still, some species produce allergy and asthma triggers.

There are hundreds of other genera of mold floating around you right now, so let’s take a look at a few of them, too.


The Stachybotrys chartarum and Stachybotrys atra species have made a name for this genus after being implicated in the symptoms of sick building syndrome and as sources of indoor airborne toxins. While certainly very toxic, Stachybotrys has never been known to infect anyone, just cause damage with toxic spores and fragments. In a recent twist, Stachybotrys species have been found to produce many compounds that show promise as pharmaceuticals.


This genus of molds can be found eating plant matter all over the world. Very few of its species can grow in any type of warm environment, so infections by Mucor are extremely rare. When it does infect immunocompromised individuals it can cause mucormycosis, a rather serious necrotizing disease.


Many of the species in this genus are known for decimating crops, but others are eaten as food. The presence of their toxins in our food is their primary threat, as they only cause rare infections in the immunocompromised.

Where to check for mold in your bathroom

Isometric drawing of a bathroom with "On the walls", "sink + toilet" and "On the floor" labeled

You may love a long, hot shower but, unfortunately, so does mold. The warm, wet environment of a bathroom is practically an invitation for mold growth. Bathrooms that lack proper ventilation (from a window, a fan, or ideally, both) are especially prone to attracting mold. While it may be clear to check for mold on shower tiles, there are plenty of less obvious places for mold to grow in the bathroom.

In the shower and bathtub

Showers and bathtubs are one of the most common places you may find bathroom mold. With repeated use, these areas tend to be damp most of the time. If you aren’t properly ventilating during and after your shower or bath, mold spores will thrive. But mold isn’t always visible and obvious; be sure to check for mold on your shampoo bottles, washcloths and loofahs, shower curtain, in and around the faucet and shower head, and in the tile grout.

The sink and toilet

The presence of water, combined with the humid nature of bathrooms, makes sinks and toilets prone to mold growth. The surface of the sink and counters, if not cleaned and dried, are the most noticeable places to check. You should also inspect toothpaste and toothbrush caddies, the tank of the toilet, behind the toilet, underneath the bathroom sink where cleaning supplies are stored (any excess moisture leftover from using the supplies can cause mold), and all of the pipes for both the sink and toilet.

In the walls and on the floor

From top to bottom, mold growth is likely in a bathroom. In addition to the places mentioned above, pay attention to any water leaks coming from the walls or floors — these leaks can cause mold to grow quickly. Bathroom rugs are also known to harbor mold, and are usually not washed as often as they should be.

Some tips to keep your bathroom free of mold

  • Use a ventilation fan during your bath or shower, and keep it on for at least 30 minutes after
  • Use a dehumidifier or air conditioner to keep humidity levels down throughout your home
  • Keep all surfaces, including counters and floors, clean and dry
  • Check for leaky faucets and pipes

Where to check for mold in your kitchen

Isometric drawing of a kitchen with "refrigerator + pantry", "in, on, + under sink", "behind stove", "microwave + stove", "trash can", and "window sills" labeled

From long-forgotten leftovers in the back of your fridge to the not so easily forgotten dishes that pile up in the sink, there are ample surfaces for mold to take up residence in your kitchen. The added levels of humidity from using the stove and running hot water from the sink can cause kitchen mold to grow quickly. Some of the most common places to check for mold in the kitchen include:

In, on, and under the kitchen sink

A lot happens in your kitchen sink. Dirty dishes pile up (it happens!), food goes through the garbage disposal, wet sponges sit in the sink or in caddies and collect bacteria, and faucets run. All of these things contribute to the potential for mold growth, so check in these areas often if you want to prevent mold. Oh, and don’t forget to check underneath the sink — leaky pipes are a big problem for mold.

The refrigerator and pantry

Food, especially if it’s expired, can cause mold. Your fridge and pantry should remain free of old food, and the surfaces should be wiped down regularly. In addition to those evident places, fridge drip trays and water dispensers collect water and are, therefore, the ideal place for mold to grow.

Microwave and stove

These food-centric places of your kitchen see a lot of food spillage and grease splatters — two things mold loves to call home. Not only is keeping these things clean and dry important for having a clean home but it’s also an easy way to prevent mold.

Other places in the kitchen

Wooden cutting boards, trash cans, behind the stove (where food crumbs fall) and windows and window sills in the kitchen are like heaven for mold spores. They feed off of these places, so keeping them clean and dry is critical for keeping mold at bay.

To keep your kitchen mold free, be sure to:

  • Ventilate when cooking and doing dishes by opening a window, using a fan, or both
  • Wash the dishes every day, so they don’t pile up in the sink
  • Clean and dry the stove top, microwave, counters, cabinets, and window sills regularly
  • Clean out the inside of your fridge and your fridge drip tray often
  • Take the trash out every day

Where to check for mold in your bedroom

Isometric drawing of a bedroom with "matress", "windows + sills", and "AC + heating vents" labeled

Generally speaking, your bedroom may not seem like a breeding ground for mold and, with properly controlled humidity, it may not be. However, all indoor spaces are susceptible to mold, so it’s worth checking for, just in case.

On your mattress

All it really takes to create mold is excess moisture and something for the mold to grow on. Finding mold on your mattress is a frightening thought. If you can, invest in a mold-resistant mattress. Otherwise, make sure your household humidity stays low and your mattress (including the underside — opt for a slatted bed frame) stays cool and dry.

Windows and window sills

As mentioned above, windows that collect condensation due to humidity can be especially problematic in preventing mold growth. If that moisture finds its way to the indoor window sill, you’re almost certain to have a mold problem. That is, unless you dry it off regularly.

Air conditioning and heating vents

You probably prefer your bedroom to be at the optimal temperature for you to get a good night’s rest. While using the AC and heating unit are fine (and can help control humidity), it’s possible for mold to grow in the vents.

To prevent mold from contaminating your bedroom, you should:

  • Use a dehumidifier to remove excess moisture from the air
  • Dry up any condensation you find on the walls and windows
  • Invest in a mold-resistant mattress or, at the very least, a waterproof mattress cover

Where to check for mold in your living room

Isometric drawing of a living room with "couch", "fireplace + chimney", "indoor plants", and "curtains" labeled

It’s clear now that mold can form in any room of your home. The living room is no exception. From meals in front of the TV to the household plants you use to keep the air fresh, the chance for mold growth is compounded with every element you add.

Couch and curtains

Fabric and upholstery do a great job of collecting mold spores. If your couch (or other cloth-covered furniture) or curtains become moist, you may notice a foul, musty smell. This should alert you to mold. However, even if it hasn’t gotten that noticeable, it’s wise to check.

Indoor plants

Greenery in your home can be good for air purification but, if not monitored, can also cause mold to grow. Ensuring your home is at an optimal humidity level and that you don’t overwater your plants should be enough to prevent this.

Fireplace and chimney

When not in use, fireplaces and chimneys are cool, damp, and dark, making them magnetic to mold spores. And because the brick used to build most fireplaces is porous, the mold can spread quickly.

Here’s how you can prevent mold from growing in your living room:

  • As always, use a dehumidifier to keep moisture levels low in your home
  • Ensure that fabric couches and curtains stay clean and dry
  • Have your chimney and fireplace cleaned by a professional

Where to check for mold in your attic, basement, and garage

You may not spend much time in these rooms of your home. Not only does this mean you’re less likely to notice mold, it also means that mold is more likely to grow due to poor ventilation. This, combined with the dark, cold nature of attics, basements, and garages, makes mold highly probable.

In the attic

Mold in the attic is a huge problem — they can contain a lot of your ventilation systems and, if left unchecked, can spread mold throughout the rest of your home. In your attic, check for mold:

  • On the roof, near any possible leaks
  • In your insulation
  • Near any vents from the kitchen, bathroom, or laundry room/dryer
  • Near your water heater or furnace
  • Around your soffit vents (these are the vents near the bottom of the roof that provide ventilation to the attic)

To prevent mold from growing (and spreading) in your attic, you can:

  • Repair any roof leaks as soon as possible
  • Use the proper type of insulation
  • Properly vent items outside, instead of into your attic
  • Keep soffit vents clear to allow air flow
  • Keeping your gutter cleaned and in good repair, especially in rainy months

In the basement

Everyone knows that musty basement smell, but your basement doesn’t have to fall victim to that odor if you keep the mold out. There are a lot of areas that are prone to mold growth here, as this tends to be a moist area of the house, so here are a few reminders on where to look for basement mold:

  • Around pipes and ducting ( look for leaks, excess moisture, and condensation)
  • Near areas where the foundation may be leaking
  • Near a sump pump
  • Windows or vents where condensation might gather

Some tips for preventing mold growth in the basement:

  • Use a dehumidifier to keep your moisture levels low
  • Paint with waterproof or mold resistant paint
  • Check and repair any leaky pipes or foundation leaks
  • Make sure there is adequate ventilation
  • Waterproof the exterior of your basement and fix drainage issues

In the garage

Rain from your car and water leaks from the roof are two of the main ways mold gets invited into your garage. If you use your garage for storage of old items or cleaning supplies, you may find mold growing in places you wouldn’t expect. Be sure to check for mold:

  • Behind or under any storage areas that don’t get moved around very often
  • Around the garage doors and windows
  • In areas where water may be standing for long periods of time

Keep mold at bay in your garage by:

  • Using a dehumidifier to keep moisture levels low, especially during wet months
  • Use a waterproof or mold and mildew resistant paint for the walls and concrete in your garage
  • Use a squeegee to remove standing water from the floor
  • Try to introduce sunlight and ventilation, when possible

Additional places to check for mold in your home

Walls and ceiling

Your walls and ceiling can hide mold behind them without you being any the wiser. Unfortunately, there isn’t an easy way to tell if there is mold in walls without paying an expert. You can, however, pay attention to a few warning signs like a musty, earthy smell or seeing condensation on the wall or ceiling. Wallpaper can also harbor mold. If you see peeling or moist wallpaper, you may have growth under the surface. Be careful about peeling it off yourself as this could release a cloud of spores. If you suspect mold growth in the walls, your best bet is to hire a professional.

Carpeting, fabric, and upholstery

As we talked about earlier, fabric surfaces are porous and known for collecting mold. There are many fabric surfaces particularly prone to mold growth: couches, curtains, clothing, and towels. Leave any of these things wet for too long and mildew will form. Once mildew is present, mold is well on its way.

Carpeting presents another issue entirely. You might not see (or smell) mold growth on your carpet but it very well could be lurking underneath on the carpet padding. Large spills and leaks happen and, when they do, should be cleaned up and thoroughly dried to prevent mold. If you do notice mold in your carpets, you may want to call a pro to handle it.

Washing machines and dryers

Appliances that use water or come into contact with it have the potential to harbor mold. Avoid keeping wet clothes in your washer or dryer and make sure that you are properly venting the dryer outside the home (and not into the attic). Front-loading washers are especially prone to mold growth, though newer models have improved this. Always use the recommended detergent and cycles to help prevent this, and keep the washer door open when not in use. Also, don’t forget to clean out the dryer lint — this, too, can grow mold.

Air conditioning and heating ducts

Your HVAC system is an extremely important place to be on the lookout for mold. If your ducting gets moldy, it can spread the spores throughout your home. You should regularly inspect your AC unit to make sure it’s draining properly and check your filters to make sure they are not wet and don’t need replacing. If you suspect mold in your ventilation system, you will likely need to contact a company that specializes in HVAC repair to clean out your system. This can be costly so be sure to talk to a few different companies; check that they have the appropriate licenses and are compliant with the National Air Duct Cleaners Association standards and get an estimate and quote in writing. This could save your health (and your wallet) in the long-run.

Worth the time invested to check

No one wants mold to grow in their home. Still, many people are unaware of the variety of common places to check for mold in their home. Initially, checking for mold and taking actions to prevent it may feel like a hassle but, in the long-run, it can prevent you from getting sick and prevent your home from being damaged.

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