How to get rid of musty smell in a house: dry it out, then clean

Step by step: how to get rid of musty smell in a house

Safety first. Wear gloves, goggles and an N-95 respirator when cleaning visible mold. If mold covers more than about 10 square feet, follows a flood or sewage backup, or is inside the HVAC system, call a professional. Never mix bleach with ammonia or other cleaners.

1. 1

   Track the smell to its source

   Sniff closets, the basement, crawl space access, under sinks, behind the washer, around the AC unit and inside cabinets on outside walls. Musty smell is strongest close to the damp spot. Look for stains, peeling paint, condensation or warped materials nearby.

2. 2

   Measure the humidity

   Put a digital hygrometer in the smelly room for a day. The EPA recommends keeping indoor humidity below 60 percent, ideally 30 to 50 percent. Readings above 60 percent mean mildew can keep growing no matter how much you clean.

3. 3

   Fix any water getting in

   Repair dripping pipes and leaking fixtures, clear gutters and point downspouts away from the foundation, and insulate cold water pipes that sweat. Dry any wet area within 24 to 48 hours, which is how fast mold can start.

4. 4

   Run a dehumidifier and ventilate

   Run a dehumidifier set to about 45 percent in basements and damp rooms, emptying or draining it daily. Use bathroom fans during and after showers and the range hood when cooking. Make sure the clothes dryer vents outdoors.

5. 5

   Scrub small mildew patches

   Wearing gloves, goggles and an N-95, scrub visible mildew on hard surfaces with dish detergent and warm water, then dry the area completely with a towel and a fan. Throw out moldy porous items such as ceiling tiles, cardboard boxes or carpet pad that cannot be cleaned.

6. 6

   Wash musty fabrics

   Wash curtains, rugs, linens and clothes that smell musty in the warmest water the labels allow, then dry them completely right away. Never leave wet laundry in the washer. Musty towels often need an extra wash; see our towel guide.

7. 7

   Air out closets and cabinets

   Empty a musty closet, wipe the walls and shelves, and leave the door open with a fan blowing in for a few hours. Leave space between stored items and outside walls, and swap cardboard boxes for plastic bins in basements.

8. 8

   Check the AC and HVAC system

   Replace the furnace filter, and check that the AC drip pan is clean and the condensate drain line is flowing. If the musty smell gets stronger when the system runs, have an HVAC technician inspect the coil and ducts.

What causes a musty smell in a house?

A musty smell is almost always mold or mildew growing somewhere damp. The smell is the warning; the moisture is the problem to fix.

The EPA’s guide to mold, moisture and your home says the key to mold control is moisture control, that you may have hidden mold if a building smells moldy and you cannot see the source, and that mold can hide on the back of drywall, wallpaper and paneling, the top of ceiling tiles and the underside of carpet and pad. Common sources:

For laundry machines, see how to clean a front load washer; for towels that smell sour even when clean, see how to get mildew smell out of towels.

Does a dehumidifier get rid of musty smell?

Yes, in most basements and damp rooms it is the single most effective step, because it stops the mildew that makes the smell. It works best once leaks are fixed.

ENERGY STAR rates dehumidifier capacity in pints per 24 hours, says the size you need depends on the room size and how damp it is, and advises that it is better to oversize than undersize. It also notes that certified models remove the same moisture as similar conventional units using about 20 percent less energy, which matters for a machine that may run all summer. Set it to around 45 percent, use the continuous drain hose if there is a floor drain, and clean the filter as the manual directs.

Will an air purifier, candles or bleach fix a musty smell?

No. They can cover the smell or kill surface growth for a while, but the musty odor returns as long as the area stays damp.

• The EPA says portable air cleaners and HVAC filters do not address the cause of mold and musty odors; you have to remove the moisture source and clean up the mold.
• The EPA’s mold cleanup advice is to scrub mold off hard surfaces with detergent and water and dry them completely, and not to paint or caulk over mold. It does not recommend bleach as a routine cleanup step, and dead mold can still cause allergic reactions, so it has to be removed, not just killed.
• Candles, plug-ins and sprays only add fragrance to the damp air.

If you find large areas of mold, see our guides to removing mold from walls and cleaning black mold, and call a professional for anything over about 10 square feet.

Mistakes to avoid

• Spraying air freshener or lighting candles without finding the damp spot.
• Cleaning mildew but leaving the humidity at 65 percent, so it grows back within weeks.
• Storing clothes and papers in cardboard boxes on a basement floor.
• Painting over mildewed walls, which peels and traps the smell.
• Leaving wet laundry in the washer overnight.
• Running the HVAC system when you suspect mold inside it, which spreads spores through the house.