Unexpected Reasons Your House Smells Musty

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A musty smell can be compared to rotting wood, wet socks, rotting vegetables, and other things that produce unpleasant odors. Sometimes the cause is obvious but other times the source is unexpected. It's important to identify where the mustiness is coming from and to eliminate it because the smell will only get worse and could cause other problems.

It's common for musty smells to be caused by moisture that has caused mold and mildew to form. But along with the offensive smell, this could affect air quality and cause allergic symptoms like sneezing, wheezing, and headaches. Even worse, molds like Aspergillus and Stachybotrys produce toxins that can be hazardous to one's health. This is why it's important to consider other sources of musty smells in one's home because certain mold growth must be removed for safety reasons.

Fortunately, most musty smells aren't dangerous and don't require professional remediation. Keep in mind that these odors can start out smelling earthy and get stronger over time. And depending on the source, the mustiness will smell different: A mildewy shower will likely smell different than a pile of sweat-soaked, unwashed clothes. Ew. And speaking of the latter, that's the first reason on this list.

Dirty laundry and hamper

Worn clothing and used linens are supposed to be tossed in hampers but they often end up on floors, furniture, and other places. Since mold can grow almost anywhere that harbors warmth and moisture, fabrics will succumb and the mildew could spread onto other surfaces. This smell can be especially potent because of the bacteria present in the fabrics.

Dirty laundry that's left too long in hampers can also start smelling musty, as can those baskets they're sitting in. To prevent these smells from developing, hang up sweaty clothes after they're worn if they won't be washed for a while. When washing smelly clothes, add a cup of baking soda or white vinegar to the machine and use the hottest setting possible. Be sure not to let it sit in the washer for too long or the musty smell will return. A smelly hamper can be cleaned with an antimicrobial spray and air-dried. Metal and plastic hampers don't absorb odors like natural materials – ones with ventilation holes and caged-shaped ones shaped work best since they allow more air to flow through.

Lack of air circulation

A room or home that has been closed up for a long time will probably smell musty when it's opened up again. With nowhere to go, humid air gets trapped inside and invites mold and mildew to set up camp. Proper air circulation minimizes moisture buildup and musty odors. When the weather permits, open up screened windows and doors to let in fresh air. But if people in the home have allergies or it's too cold outside, turn on fans and run them often instead.

Cross-breezes are especially good for ventilating musty-smelling homes. This is when a door or window is opened on both sides of a house, like a front and back door. Do this in the early morning or evening, especially when the weather is hot. This can even help cut down on utility costs. And remember to check rooms that aren't used that often – open those windows or turn on fans for a few hours every couple of days at the minimum.

Lingering smoke from cigarettes

Cigarette, cigar, and pipe smoke penetrate soft and hard surfaces like drywall, furniture, curtains, and rugs and is hard to remove. Smokers get used to the smell but others recognize it immediately. It's not something that goes away after a few days, either– the mustiness can linger for decades

Known as thirdhand smoke (THS), this residue contains tiny particles of tobacco, nicotine, tars, and resins that work their way into everything A study in the journal Toxics warns that THS contains heavy metals and toxic particulates that cause cancer. The levels can stay high even after indoor smoking has stopped. Burning candles and opening windows provide little help. To remove leftover cigarette smoke, launder fabrics and clean the rugs or carpets with vinegar or baking soda. Some homeowners place bowls of activated charcoal in rooms and spray Febreeze, too. If the musty, smoky smell has gotten into the walls, they may need to be repainted.

Clothes that were folded and put away when damp

Washing and drying laundry takes time and should never be rushed. And even though it's annoying when the dryer completes a cycle and the clothes or linens aren't totally dry, it's never a good idea to take them out and fold them. People think this saves time and the items will dry on their own, but neither is true. Once damp fabric is folded up, mildew can grow right in the folds – it's the perfect damp, warm, and dark environment. This is why a musty smell can come from inside a linen closet, drawer, or anywhere else where folded fabrics lie.

To keep your closet smelling fresh, always check things when they come out of the dryer. Whenever anything feels damp, toss it back in for a few more minutes or hang it up to air-dry. No one wants to reach for a t-shirt only to discover that it smells – rushing through laundry chores inevitably leads to having to rewash things.

Pet stains weren't removed from the floor

Dogs and cats can be kind of sneaky, leaving unmentionables in hidden areas when no one is watching. And if the "gift" isn't found for a while, it will develop a rank, musty smell. Not only can this lead to mold and bacteria growth on a floor or carpet, but it can also penetrate down into the carpet pad and subfloor beneath.

The smell of pet urine can be especially hard to remove because of its composition. Cat and dog pee have high levels of uric acid that turn into crystal form. On top of that, cat urine contains a distinctly potent-smelling amino acid. Removing the residue is important – besides the possibility of mold growth and stench, it can also cause permanent discoloration and damage. Regular cleaning products aren't usually effective on stubborn pet smells so look for one that's safe and specifically designed to remove them. And remember to change the cat's litter box often. Otherwise, it will smell terrible and the cat will start doing its business elsewhere in the house.

The refrigerator might be the problem

The thought of eating moldy food can be stomach-turning but refrigerators are common breeding grounds for the stuff. The musty odors inside come from mold and bacteria that can take over when there is enough moisture present. The dampness could be a symptom of humidity in the room, condensation inside the fridge, or rotten and spilled food. The mess can be hidden in far corners where it isn't easily seen, and the growth might not be noticed until the musty smell announces its presence.

A good cleaning can eliminate the odor and preventative measures can keep it from coming back. Silicone mats can keep produce fresher for longer and sometimes, turning the fridge temperature down will prevent the interior from becoming too humid. The best temperature is 35 to 37 degrees Fahrenheit, but it might need to be lower than that. Invest in a refrigerator thermometer if there isn't one built into the appliance. And as a final tip, wipe up spills and splatters immediately and clean the fridge once a week.

It's coming from the washing machine

A washing machine could also be an expected source of a musty smell, even when it looks perfectly fine on the outside. It can happen to top- and-front-loading washers, but the second kind is more prone to it. That's because they have hard-to-reach areas like rubber gasket seals that might not dry out quickly. A laundry drain can also harbor mold and mildew since it constantly has water flowing through it.

Run an empty hot water cycle to eradicate a musty smell from a washer. But instead of adding detergent, use half a cup of baking soda and two cups of vinegar. The other option is to use half a cup of bleach but that liquid is harsher. When using bleach, fill the washing machine with water before adding it. And to prevent a musty smell from forming again, wipe down the interior once in a while, keep the washer door open between cycles, and only use the recommended amount of detergent. Adding in more won't get the laundry any cleaner and can cause buildup.

The HVAC system hasn't been cleaned out

Home heating and cooling systems have plenty of working parts that can trap dirt, dust, and moisture. When they aren't maintained properly, the air flowing through can be distributed into the rooms of a house. It's common for an air conditioner to put out stale-smelling air when it's first used at the start of a season, because of mold buildup on the filters. To avoid the musty smell, and help your HVAC system work more efficiently, it's best to change the filters every three months (more often if you have pets). Other easy fixes include emptying the drain pan and cleaning the outside of the vents.

If none of those eliminate the smell, the unit's coils could be moldy or frozen. Those should be cleaned by an HVAC professional for safety reasons. Also, hire a contractor if the ducts need to be cleaned or a drain line is clogged. Signs of these kinds of problems include the unit not working efficiently and pools of standing water near the unit.

It's coming from the dust

Dust builds up on every surface imaginable and guess what – too much of it makes homes smell musty. That's because it contains things like dead skin cells, dirt, pet hair, and allergens like pollen and dust mites. These accumulations can be cleaned up with vacuums and DIY or store-bought products, but pay attention to the harder-to-reach areas. Dry rubber sponges are good for removing dust and dirt from walls, and rugs and carpets can be laundered or shampooed to remove odors.

Long-handled dusters can also be good for removing dust but go over the surface with a damp cloth afterward to be sure you're getting all of the dust. Clean hard floors with damp mops after sweeping them and be sure to get into the corners. And to reduce dust buildup, do a hard de-cluttering. Things like stuffed animals and tchotchkes are notorious dust collectors so it might make sense to put them away or donate them.

Leaky pipes

When a kitchen or bathroom smells musty, the culprit might very well be a leaky pipe. The red flags for this include suddenly high water bills, a pool of water by the pipe, damp marks on walls, and the sound of water rushing through the pipes when everything has been shut off. Since the water's constantly leaking out, it doesn't dry, resulting in a musty odor.

Once the leaky pipe has been identified, it could be a simple repair. To get started, turn off the main water valve, open up the faucets, and flush all the toilets to empty any water. Wipe the pipe down with a wet cloth and wipe it dry. One of the easiest ways to repair a leaking pipe is to cover up the damaged area with fiberglass tape, but be warned that this might only be a temporary fix. It might also be possible to tighten things up with a wrench.

Epoxy putty can also work since it hardens onto the surface. Once the pipe is wiped clean, it should be sanded down to smooth out the damage. This kind of putty may need to be mixed with water first but no matter which kind of epoxy is used, it must be applied quickly before it dries. It also needs to sit on the pipe for about an hour before the water can be turned on again. For serious pipe leaks, it's safer to call a licensed plumber.

Water coming in through the roof

A homeowner might not realize that their roof leaks, particularly when it's located above a garage or room that's not used often. Telltale signs include water spots on walls and ceilings, clogged soffits, rusted gutters, mold where the roof meets an exterior wall, and that musty smell.

The source of the leak could be something simple like a few broken shingles or be more involved. If the problem is detected early enough, it could be a quick fix to be completed by a roofing professional. Even small leaks can be labor-intensive repairs though, and any kind of roof damage should be taken seriously. When a roof leak isn't attended to early and gets worse, the water can damage attic insulation, furniture, walls, and floors. If it can't be patched or repaired in another way, a new roof might be the only answer.

Moisture in the basement

Unfinished basements aren't used as often as finished ones and this means that a musty basement smell could go undetected for ages. The darkness and dampness create the perfect setting for mold growth and even if the basement only smells after a good rain, the underlying problem is still there. Some of the most common spots for mold growth in basements include beneath storage areas, around the furnace and water heater, basement windows, and vents. Moisture can also get in through cracks in the floors and walls.

To address this problem, seal up any leaks and clean the mold stains with bleach and a cleaning brush. Throw away anything that has mold growing on it and be sure to check cardboard boxes and anything with fabric. Damaged drywall may have to be taken down and replaced. It's also a good idea to put a dehumidifier in your basement – the optimum humidity level should be from 45 to 55%.

Home accessories and fabrics

Any fabrics exposed to moisture are at risk of developing musty odors. This underscores the importance of regularly washing and drying bath rugs and bath towels. But don't forget about cleaning the curtains, especially ones close to showers, tubs, and sinks. It's a good idea to replace old ones with newer, washable ones that can be cleaned in the laundry room.

Moisture and dust also accumulate on curtains in other rooms but these can be harder to clean. They can be taken down and dry-cleaned, and that's a good time to check the windows for repairable leaks. Upholstered furniture can also get damp and dusty and this can get out of control when there are pets in the house. They can be regularly cleaned with products like Resolve Upholstery and Multi-Fabric Cleaner, but they need to dry out afterward – removing the cushions when possible and using fans helps.

Bringing in furniture from the garage

Furniture that's been stored in garages and sheds can develop musty smells after being cooped up for so long. This applies to outdoor patio furniture plus pieces that were put away for other reasons. Unless the pieces are properly cleaned, homeowners might be bringing mold and mustiness into their homes. The furniture materials most likely to encourage mildew growth are wood and fabric but as long as there's moisture... you get the point. So if you recently brought stored furniture indoors, there might be an accompanying musty odor. It will be less noticeable with outdoor furniture since it's not enclosed indoors.

Still, sitting on moldy furniture is gross no matter where it is. Whenever you take out stored furniture, check each piece carefully from top to bottom. It might be salvageable after a thorough cleaning but a serious mold infestation will ruin it. Before storing furniture, clean it first and keep it away from doors, walls, and windows. Don't arrange the pieces too close together to allow for air circulation, and protect them with a moisture barrier. Moisture barriers can be made from plastic sheets or tarps.