Why Does My Room Smell Musty? Causes and How to Get Rid of the Smell

A room smells musty because of moisture. When a room stays damp, mold and mildew start to grow, often in places you cannot see. As they grow, they give off a stale, earthy smell, a bit like wet cardboard or an old basement.

So the fix is not an air freshener. The fix is to find where the moisture is coming from, dry the room out, and clean up any mold or mildew. Once the room stays dry, the smell goes away and stays away.

This guide will help you find the cause, get rid of the smell step by step, and keep it from coming back.

What causes a musty smell?

That musty smell comes from gases that mold and mildew give off as they grow. Mold and mildew are types of fungus. They need three things to grow:

• Moisture, from damp air, leaks, or wet materials
• Food, like wood, paper, drywall, fabric, dust, or soap scum
• Time, usually just a day or two of dampness

You can smell mold long before you see it. That is why a musty smell is a helpful early warning.

8 common reasons your room smells musty

1. The room does not get enough fresh air

Rooms that stay closed up hold in moisture. Every time you breathe, shower, or cook, water goes into the air. Without fresh air, that moisture has nowhere to go. Guest rooms, basements, and rooms with windows that never open are the most common problem spots.

2. Condensation on windows and walls

Do you see water drops on the inside of your windows in the morning? That is condensation. It happens when warm, damp air touches a cold surface and turns back into water. Over time, it soaks into window frames, walls, and corners. You might see black spots near windows or in corners behind furniture. This is very common in bedrooms during cold weather.

3. Drying laundry inside

A load of wet laundry lets off a lot of water as it dries. Drying clothes on a rack in a closed room is one of the fastest ways to make a room damp and musty.

4. A hidden leak

A slow leak from a roof, gutter, window seal, pipe, or radiator can soak into walls, ceilings, or floors without you noticing. Look for:

• Stains on the ceiling or walls
• Peeling paint or bubbling wallpaper
• Warped baseboards
• A floor that feels soft or spongy
• A musty smell that is strongest in one spot

5. Carpet, furniture, and stored items

Carpets, mattresses, couches, curtains, and boxes of stored clothes soak up moisture and smells. Items stored against cold outside walls are more likely to get mildew. Old carpet in a basement often smells musty even when the air feels fine.

6. Your air conditioner

Window units and other air conditioners pull water out of the air. That water drips into a tray and drains away. If the tray or drain gets blocked, or the coils are dirty, water sits inside the unit. Then a musty smell blows out when the AC runs.

7. Basements and ground floors

Rooms below or at ground level are cooler, and moisture can seep in through the walls and floor. That is why basements are often damp and musty, even without a leak.

8. Your closet is too full

Packed closets do not get any air. If clothes go into the closet a little damp, or the closet is on an outside wall, it can start to smell musty.

Musty smell or something else?

Different smells point to different problems. Use this table to make sure you are fixing the right thing.

If the smell does not fit any of these, or you cannot find the cause, a home inspector can help track it down.

How to find the source of a musty smell

Follow these steps to track down the cause.

1. Follow your nose. The smell is usually strongest near the source. Sniff inside closets, behind furniture, under sinks, near windows, and in corners.
2. Check the humidity. A small digital hygrometer costs just a few dollars. It tells you how damp the air is. If it reads above 60% most of the time, the air itself is the problem.
3. Look for signs of mold: black, green, gray, or white spots; fuzzy patches; or stains.
4. Move furniture away from the walls and look behind it, especially on outside walls.
5. Check under sinks and around the bathtub, shower, and toilet for drips.
6. Look at the ceiling for stains that could mean a roof or pipe leak.
7. Check your air conditioner's drip tray and filter.

If the smell is more like a sewer than damp, the cause is usually a drain or toilet instead. See our guide on why a house can smell like sewage.

How to get rid of a musty smell step by step

Step 1: Fix any water problem first

This is the most important step. Repair leaks, clean clogged gutters, reseal windows, and fix dripping pipes. Nothing else will work for long until the water stops.

Step 2: Dry the room out

• Open windows for at least 10 to 15 minutes every day. If you can, open windows on opposite sides of the room or home to create a cross breeze.
• Run a dehumidifier until the humidity is below 50%. Empty the water tank often.
• Use exhaust fans while cooking and showering, and leave them on for 15 to 20 minutes afterward.
• Move furniture a few inches away from outside walls so air can flow behind it.
• Run the air conditioner in hot, humid weather. It removes moisture as it cools.

Step 3: Clean small areas of mold or mildew

For small spots on hard surfaces, like tile, glass, or painted walls:

1. Put on rubber gloves, safety glasses, and a mask.
2. Open a window.
3. Scrub the area with water and dish soap or a household cleaner.
4. Rinse and dry the surface completely.

The EPA says you can usually clean mold yourself if the area is smaller than about 10 square feet, which is about a 3-foot by 3-foot patch.

Step 4: Clean fabrics and soft furniture

• Wash curtains, bedding, pillow covers, and clothes on the hottest setting the labels allow.
• Dry them completely, outside in the sun if you can.
• For carpet and mattresses, sprinkle baking soda over the surface. Leave it for several hours or overnight. Then vacuum it up well.
• Badly mildewed carpet or carpet padding may need to be replaced.

Step 5: Soak up what is left

Once the cause is fixed, you can soak up any leftover smell with:

• Bowls of baking soda placed around the room
• Bags of activated charcoal
• Fresh air and sunlight

These help clear the last of the smell. But they will not fix the problem if the room is still damp.

How to get rid of a musty smell in specific places

In a closet

Take everything out. Wipe the walls and shelves. Wash or air out the clothes. Leave the door open for a day, and run a dehumidifier or fan nearby. Put everything back loosely so air can flow. A small box of baking soda or a moisture absorber on the shelf helps.

In a basement

Basements need extra help. Run a dehumidifier all the time in damp months. Make sure gutters and downspouts carry rain water away from the house. Keep boxes off the floor on plastic shelves, and use plastic bins instead of cardboard.

From an air conditioner

Turn off the unit and unplug it. Clean or replace the filter. Clean the drip tray and make sure the drain is not clogged. For bad smells or central air systems, call a heating and cooling technician.

In clothes and towels

Rewash them in hot water with a cup of white vinegar added to the rinse. Dry them fully right away. Never leave wet laundry sitting in the washer.

How to keep the musty smell from coming back

• Keep humidity between 30% and 50%, and check it with a hygrometer.
• Dry laundry outside or in the dryer. If you must dry it inside, use a small room with the door shut, the window open, and a dehumidifier running.
• Open windows every day, even in winter. A few minutes with the window wide open is better than a window cracked all day.
• Use exhaust fans in the kitchen and bathroom.
• Keep furniture a few inches from outside walls.
• Do not overpack closets.
• Fix leaks right away.
• Clean your air conditioner drip trays and filters as the maker suggests.

Damp homes often feel dusty too, because dust mites love humid air. If that sounds familiar, see our guide on why your house gets so dusty and how to fix it.

When to call a professional

Call a mold specialist, plumber, roofer, or contractor if:

• You find a hidden leak
• Mold covers more than about 10 square feet
• Mold keeps coming back after cleaning
• You see rotting wood or soft floors
• Damp patches keep spreading
• Anyone in your home has worsening breathing problems

If you rent your home, tell your landlord about damp and mold in writing as soon as you notice it.

The bottom line

A musty smell almost always means moisture and mold or mildew somewhere nearby. Find the source first, and fix any leaks. Then dry the room with fresh air, a dehumidifier, and exhaust fans. Clean small mold spots, wash fabrics, and use baking soda to soak up what is left. Keep the humidity below 50%, and the musty smell will stay gone.