What Does Mold Smell Like? Musty, Earthy Odors Explained
What does mold smell like? Usually musty, earthy and damp, like wet cardboard. See how to tell it from sewer or gas smells and how to find the hidden source.
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** Most people describe it as musty, earthy and damp, like wet cardboard, old socks, a damp basement or rotting wood. Some say it is sour or like dirty laundry. The smell comes from gases mold gives off as it grows, and it is often strongest in closed spaces. A musty smell can mean mold even when you cannot see any.
ven when you cannot see any.
What does mold smell like: the common descriptions
The odor of mold is hard to pin down, because it depends on the species, the material and how much is growing. The words people use most are musty, earthy, stale, damp and sour. If a room smells like a wet basement even when everything looks dry, hidden moisture is a likely cause.
| Quick facts: what does mold smell like | |
|---|---|
| Typical description | Musty, earthy, damp, like wet cardboard or old socks |
| Strongest when | Rooms are closed, humid or warm; after rain or a leak |
| No smell, still mold? | Yes, mold can grow with little or no odor |
| Do not rely on smell alone | Other problems smell similar |
Other smells that get mistaken for mold
| Smell | Possible cause |
|---|---|
| Musty, earthy | Mold, mildew, damp materials |
| Rotten eggs | Sewer gas or natural gas additive; leave the house if it is strong and call the gas company |
| Sewage | Dry trap, broken vent, sewer problem |
| Sour milk | Bacteria in a drain, washing machine or dishwasher |
| Dusty burning smell | Heater or electrical issue, not mold |
| Dead animal | Animal in a wall or vent |
If you smell rotten eggs strongly, leave the building and call your gas utility from outside. Do not turn lights or appliances on or off.
How to find the source
- Follow the smell. Walk from room to room with windows closed and note where it is strongest.
- Check wet areas. Look under sinks, behind the toilet and around the water heater and washing machine for leaks and stains.
- Look for stains and bubbling. Ceilings, walls and floors can hide damp patches.
- Check humidity. A cheap hygrometer shows if the room stays above about 60 percent.
- Use a moisture meter on walls and floors to find damp areas you cannot see.
- Inspect storage. Cardboard boxes, old books and fabric in basements and closets hold moisture.
Common hiding places
Behind wallpaper and baseboards, under flooring, inside wall cavities, above ceiling tiles, in crawl spaces and in HVAC ducts and drip pans. Appliances such as washing machines, dishwashers and dehumidifiers can also develop mildew smells that spread through a room.
What to do about the smell
Find and fix the moisture, dry the area, and clean or remove moldy materials. Air fresheners and sprays only hide the odor. Run a dehumidifier to keep humidity between 30 and 50 percent, and use fans or open windows when conditions allow. Throw out porous items that stay musty after drying.
Health effects of the smell
Mold odors can irritate some people, cause headaches or trigger allergy and asthma symptoms. The smell itself does not tell you the species or how risky it is. If symptoms ease when you leave the house, mention it to your doctor.
When the smell comes and goes
A smell that appears only on humid days, after rain or when the heating or air conditioning starts usually points to hidden damp rather than an open leak. Air moving through ducts, vents and wall cavities pulls odor into the room. If the smell is worse in one cupboard, closet or room, start the search there and look behind furniture, which blocks airflow and traps humidity against cool outer walls. Keep a note of when the odor is strongest, because the pattern helps a professional find the source.
When to call a professional
If the smell persists after you dry and clean, comes from walls or floors, follows a leak or flood, or you have health symptoms, call a mold specialist or water damage company. Understanding what does mold smell like helps you spot it early, but finding the cause is what ends it.
Related reading
- Basement Smells Musty After Rain: Causes and How to Fix It
- Mold After Water Damage: How Fast It Grows and What to Do
- Sewer Smell in House: Causes, Fixes and Safety Warnings
- Moisture Meter for Walls: How to Use One and Read the Numbers
Browse all water damage guides, or find a water damage restoration company in your city from the water damage directory.
Frequently asked questions
What does mold smell like?
Most people describe a musty, earthy, damp smell like wet cardboard, old socks or a damp basement. Some find it sour or like dirty laundry. It is often strongest in closed, humid rooms.
Can I have mold if I cannot see it but smell it?
Yes. Mold can grow behind walls, under flooring or above ceilings. A persistent musty smell is a good reason to check for leaks, damp and condensation, and to use a moisture meter if you have one.
Does mold always smell?
No. Some molds give off little or no odor, so a lack of smell does not prove a clean house. Visible growth, stains, dampness and humidity readings are better signs than smell alone.
How can I tell mold smell from sewer smell?
Mold usually smells musty or earthy, while sewer gas smells like rotten eggs or sewage. Strong rotten egg smells can also mean a gas leak, so leave the house and call the gas company if it is strong.
Why does my house smell musty after it rains?
Rain can raise humidity and bring moisture into basements, crawl spaces and walls through leaks or poor drainage. Check for damp spots, gutter problems and cracks, and use a dehumidifier to dry the air.
What does mold smell like in a basement?
A damp, earthy, stale odor, often like wet soil or cardboard. It may be stronger after rain or in summer. Look for leaks, condensation on cold pipes, stained walls and stored boxes that feel damp.
How do I get rid of a mold smell?
Find and fix the water source, dry the area, clean hard surfaces and remove porous materials that are moldy. Air fresheners only mask the smell. A dehumidifier and ventilation help keep it from returning.
Can mold smell make you sick?
The odor can irritate some people and trigger headaches or allergy and asthma symptoms. The smell does not tell you how risky the mold is. If symptoms ease away from home, tell your doctor.
Is a musty smell always mold?
No. It can also come from damp fabrics, mildew, dirty drains or old materials. Because the causes look alike, check for moisture and visible growth rather than guessing from the smell.
When should I call a professional about a mold smell?
Call if the smell persists after drying and cleaning, seems to come from walls or floors, follows a leak or flood or comes with health symptoms. A specialist can locate hidden mold and moisture.
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