How to remove musty smell from a house

Step by step

1. 1

   Follow your nose to the source

   Walk the house and note where the smell is strongest: a bathroom, a closet on an outside wall, under a sink, the basement, a laundry room or near a window. Look for leaks, condensation, water stains and visible mold.

   Why: A musty smell means mold is growing nearby. Finding where is the whole job.

2. 2

   Check the hidden places

   If you smell mold but can't see it, check behind furniture against outside walls, under sinks, behind wallpaper or paneling, the top of ceiling tiles, under carpet and pad, and around HVAC ducts and vents.

   Why: EPA lists these as common hiding places for mold. A smell with no visible growth points to one of them.

3. 3

   Fix the moisture

   Repair leaks, run bathroom and kitchen exhaust fans, vent the dryer outside, and use a dehumidifier to bring humidity below 60%, ideally 30 to 50%.

   Why: Mold can't grow without moisture. Until the damp is fixed, cleaning only buys a few weeks.

4. 4

   Clean mold off hard surfaces

   Wearing an N-95 respirator, gloves and non-vented goggles, scrub mold off hard surfaces with detergent and water, then dry them completely.

   Why: The mold has to be physically removed. Killing it isn't enough, because dead mold can still cause allergic reactions.

5. 5

   Replace what stays moldy

   Throw out and replace absorbent materials that stay moldy after cleaning, such as ceiling tiles, carpet padding or drywall. For areas over about 10 square feet, follow EPA's larger-scale guidance or hire a professional.

   Why: Mold grows into porous materials where cleaning can't reach, and they'll keep smelling.

6. 6

   Wash fabrics and air out closets

   Wash musty linens, curtains and clothes in the hottest water they allow. Leave closet doors open, and put open containers of baking soda or activated charcoal in closets and cupboards.

   Why: Fabrics hold the musty smell after the source is fixed. Airflow and adsorbents clear what's left in enclosed spaces.

What a musty smell in a house means

A musty or moldy smell comes from microbial volatile organic compounds given off by growing mold. EPA treats it as a sign of mold growth that should be investigated, even if you can't see any. Mold needs moisture, so the smell always traces back to damp: a leak, condensation on cold walls or windows, a humid bathroom, wet carpet, or ground moisture in a basement.

That's why fresheners never solve it. They cover the smell while the mold keeps growing. EPA says cleanup isn't finished until the moisture problem is fixed and the visible mold and moldy odors are gone. See the mildew smell page for the science.

Keeping humidity down

EPA recommends indoor relative humidity below 60%, ideally between 30 and 50%. A humidity meter shows where you stand. Run exhaust fans when showering, cooking and running the dishwasher, vent clothes dryers to the outdoors, and use a dehumidifier in damp rooms.

Wet materials dried within 24 to 48 hours usually don't grow mold, so act quickly after any spill, leak or flood.

By situation

Musty smell in one closet

Closets get little airflow, and damp items stored inside make it worse. Empty it, check for mold on the walls and floor, wash the contents, and leave the door open with a container of baking soda or charcoal inside. A dehumidifier nearby helps.

Musty bathroom

Mildew feeds on soap scum. Clean tile, grout and the shower curtain with detergent and water, run the exhaust fan during and after showers, and hang towels to dry spread out.

Musty smell from the basement

Basements are below grade and naturally damp. See musty smell in a basement for the specific steps.

Musty carpet

Wet pad or a damp slab is the usual cause. See mildew smell in carpet.

Musty smell when the AC or heat runs

Mold can grow inside ductwork. Check the filter and around vents, and have the system inspected if the smell comes from the ducts.

After a flood or major leak

Dry everything within 24 to 48 hours if possible, remove soaked absorbent materials, and get professional help for large areas.

What not to do

• Don't cover a musty smell with air freshener. The smell is a sign of mold growth that keeps going underneath.
• Don't paint over mold. EPA says mold must be cleaned off and surfaces dried before painting, or the paint will peel.
• Don't rely on bleach for routine mold cleanup. EPA recommends detergent and water and doesn't recommend routine use of biocides. Never mix bleach with ammonia.
• Don't touch mold with bare hands or clean it without a mask. Mold exposure can cause allergic reactions and breathing problems.

Other methods that work

Professional mold remediation

For mold over about 10 square feet, after major water damage, or mold in HVAC ducts, a professional following EPA guidance is the safer route.

Activated charcoal or baking soda

Open containers in closets and cupboards absorb lingering musty odor once the source is fixed.

Caution: They don't fix damp or kill mold.

Stain still there?

The smell keeps coming back

The moisture source isn't fixed, or mold is hidden. Check humidity, look behind and under things, and consider a professional inspection.

It smells musty only in summer

Summer humidity is feeding growth. Run a dehumidifier and keep humidity below 60%.

Safety

• Wear an N-95 respirator, long gloves and goggles without vent holes when cleaning mold.
• Mold exposure can worsen asthma and allergies, and mVOCs have been linked to headaches, dizziness and nausea.
• Ventilate when using any cleaner, and never mix bleach with ammonia or acids.

Never mix cleaning products; see chemicals you must never combine.

Questions

Mildew elsewhere

• Mildew: what causes it and how to remove it
• Mildew in a basement
• Mildew in a car
• Mildew in carpet
• Mildew in clothes
• Mildew in towels
• Mildew in a washing machine

Other smells in the house

• How to remove burnt smell from your house (burnt popcorn too)
• How to remove fish smell from your house
• How to remove dog smell (and cat smell) from your house
• How to remove skunk smell from your house
• How to remove smoke smell from a house (cigarette or fire)