Musty Smell in Rugs: Find the Cause and Get Rid of Mildew Odor

A musty smell in rugs is a moisture problem before it is an odor problem, and in South Florida the air itself can supply the moisture. Sprays and powders may cover the smell for a while, but it comes back until the source is fixed. This guide shows how to find that source, what you can safely do at home, and when a rug needs a full wash.

What Causes a Musty Smell in Rugs?

A musty smell is the byproduct of mold, mildew or bacteria growing on fibers that stayed damp. Smithsonian textile conservation guidance traces musty odors to volatile compounds these organisms release. Mildew is the everyday name for mold on damp household surfaces and fabrics, and it needs moisture plus something to feed on, such as soil, spills or the fibers themselves.

Rugs are prone to it because natural fibers absorb water quickly and release it slowly. In still air, mold can grow on cotton once relative humidity (the moisture in the air compared with the most it can hold at that temperature) passes about 80 percent, while wool and silk hold out until about 92 percent. Synthetics such as polyester and nylon absorb little moisture.

Many hand-knotted wool rugs are woven on a cotton foundation, the warp and weft threads that hold the pile, the yarn you walk on. The pile can feel dry while the cotton underneath is still damp. That fits University of Georgia Extension's observation that mildew usually grows first on the back, and it explains why the smell can outlast a clean-looking surface.

Why Does Your Rug Smell Like Mildew? Find the Source First

If your rug smells like mildew, one of five moisture sources is usually behind it, and each needs a different fix. Narrow it down before you buy any product.

Quick test: Fold back a corner and smell the back. If it smells stronger than the face, the problem is in the foundation, and sprays or powders on the surface will not reach it.

Damp Pad or Floor

The U.S. Environmental Protection Agency (EPA) lists the underside of carpets and pads among the places mold hides. Check for leaks near doors, the air handler and appliances, and keep the rug off the spot until the pad and floor are dry. If the pad is past saving, see how to choose a rug pad.

Pet Accidents

Urine that reaches the foundation keeps smelling until it is washed out. Spills and soil add to the problem, because Smithsonian guidance notes that organic residue lets mold grow at lower humidity than a clean textile would need. Our guide to removing pet urine from a rug covers fresh and old accidents.

Storage

A rug rolled up in plastic, or kept in a garage, attic or closet against an exterior wall, often comes out musty. Smithsonian guidance advises against attics and closets on exterior walls for textiles because temperature and humidity swing there. Before you put a rug away again, read how to store a rug.

How to Get Mildew Smell Out of a Rug

Dry first and deodorize last: odor treatments only work once the rug, the pad and the room are dry and stay that way.

1. Lift it off the source. Raise the rug on clean, dry supports, or fold it back in sections, so air reaches the back, as University of Georgia Extension recommends.
2. Dry the air, not just the rug. On muggy days, keep windows closed and run the air conditioning or a dehumidifier. Point fans across and under the rug, but not straight at worn or weakened spots.
3. Work fast. EPA says damp materials dried within 24 to 48 hours of a leak or spill usually will not grow mold. The rug is not dry until the foundation is, so check the back by hand.
4. Sun the back, not the face. Virginia Cooperative Extension recommends exposing the back of a mildewed rug to direct sunlight. On a dry, breezy day, lay sturdy wool or synthetic rugs face down on a clean surface to shield the colors from sun fading; skip this for silk, viscose and antique rugs.
5. Vacuum both sides once dry. Gentle vacuuming lifts dried mold residue. Empty the canister or bag outdoors right away, as University of Georgia Extension advises, so spores are not scattered indoors.
6. Air it out before you reach for a product. Smithsonian guidance says warm, dry airing helps a musty smell dissipate, and warns that commercial odor products may make dyes bleed or dull a finish. If you try one, test it in an inconspicuous spot first, and skip powders on handmade rugs: Southwest Looms, a rug maker, warns that powders leave gritty residue behind.

What Indoor Humidity Keeps a Rug From Smelling Musty?

Keep indoor relative humidity between 30 and 50 percent, and do not let it sit above 60 percent. The numbers that matter:

• 30 to 50 percent: EPA's ideal indoor range; the agency advises keeping humidity below 60 percent and using air conditioners or dehumidifiers when needed.
• 75 to 85 degrees Fahrenheit: where Virginia Cooperative Extension says most mildew growth occurs, so in a warm climate, moisture is the lever you control.
• About 80 percent in still air: enough for mold on cotton, the fiber in many rug foundations.

In South Florida, the trap is a room that feels cool but stays damp. Smithsonian guidance notes that humid air that is cooled without being dehumidified ends up with very high relative humidity, so trust a humidity meter over the thermostat.

Where a rug has to live in a damp spot, Virginia Cooperative Extension recommends one with synthetic fibers in both the face and the backing. For year-round climate care, see rug care in Miami humidity, salt air and sun.

Why a Rug Smells After Cleaning

When a rug smells after cleaning, the usual reason is that it stayed wet too long and mildew got a start in the foundation. The common culprits:

• Washing it, or wetting it with a rented carpet cleaner, when it cannot dry within 24 to 48 hours.
• Drying it flat on a floor, patio or lawn, where the back cannot breathe.
• Rolling it up or putting it back on its pad before the foundation was dry.
• Using more water than you could extract, so the foundation stays wet after the pile feels dry.
• Dampening, but not washing out, an old spill or pet accident that then feeds mildew.

A faint damp smell while a rug finishes drying is normal. If the odor is still there once the rug is completely dry, or grows stronger over the next few days, treat it as mildew and go back to the steps above. If the rug is still wet now, follow our guide on how to dry a wet rug.

What Not to Do With a Musty Rug

Do not mask the smell, bleach the rug or add more water than you can remove within a day or two.

• Fragrance sprays and air fresheners. They hide the odor without stopping the growth; Virginia Cooperative Extension notes they have to be used continually.
• Bleach and ammonia. The Carpet and Rug Institute warns that bleaching agents can destroy carpet color and damage fibers, and University of Georgia Extension warns that ammonia damages silk and wool.
• Hydrogen peroxide. Some guides suggest a dilute solution on the back of a mildewed rug, but it is a bleaching agent that can lighten dyes.
• Steam cleaning. Southwest Looms warns that steam can make dyes bleed and shrink wool.
• Hard scrubbing. Smithsonian guidance notes that mildewed areas are weaker than the rest of a textile, and agitation can turn weak spots into tears.
• Wrapping or storing it damp. Plastic traps moisture, so store a rug only when it is clean and completely dry.

When to Call a Professional

Call a professional when the smell lives in the foundation, because home steps treat the surface while the source stays inside the rug. Signs it is time:

• The odor returns after the rug is dry and humidity is under control.
• The back smells stronger than the face or shows dark spotting.
• The rug is silk, viscose, antique or an heirloom.
• A pet accident reached the foundation.
• The rug is too large or thick to dry at home within 24 to 48 hours.
• Some areas feel stiff, brittle or weaker than the rest.

A thorough wash reaches the foundation, where surface treatments cannot, and controlled drying matters just as much, because a rug that dries slowly can start smelling again. At Bakers Rug Service, every rug is washed by hand, individually, and never machine cleaned. We inspect it for dye stability, stains and structural damage, deep-dust it to remove embedded dry soil, hand-wash it with gentle pH-neutral solutions, and handle repairs if you ask. Then it is air-dried in a climate-controlled environment to prevent mold and shrinkage.

Our rug washing and repair services also include pet stain and odor treatment. Estimates are free, and from our shop at 8723 SW 132 St in the Kendall area we offer complimentary pickup and delivery across Miami-Dade, Broward and Palm Beach counties, including South Miami and Doral. Call (305) 232-3368 or tell us about your rug to find out whether yours can be handled at home.