A musty odor is usually caused by mold or mildew from moisture and poor ventilation.
Causes
- Mold and mildew.
- Moisture or leaks.
- Poor ventilation.
- Damp basements.
- Wet clothes or towels.
- Old books and fabrics.
Health
Mold can trigger allergies and asthma.
Fix
- Find and fix the leak.
- Use a dehumidifier (keep humidity under 50%).
- Clean with vinegar or detergent.
- Ventilate.
Call a pro
For large mold areas over 10 square feet.
Source of the smell
Musty odor comes from mold and mildew growing in damp spaces, and from microbial volatile organic compounds (MVOCs). Common sources include water leaks, high humidity, poor ventilation, wet carpet, basements, crawl spaces, damp towels and clothes, and HVAC systems with condensation.
- The EPA recommends keeping indoor humidity below 60 percent, ideally 30 to 50 percent.
- Mold can grow within 24 to 48 hours on wet surfaces.
- Hidden mold may be behind walls, under flooring or in attics.
Health and fix
Mold exposure can cause nasal congestion, wheezing, coughing and skin or eye irritation, especially in people with asthma or allergies. Fix the water source, dry the area within 48 hours, run a dehumidifier, improve ventilation and clean hard surfaces with detergent and water. Replace porous materials that stay moldy. Call a professional for mold over about 10 square feet, contamination after flooding or sewage, or a persistent odor with no visible source.
Source of the smell
Musty odor comes from mold and mildew growing in damp places, such as basements and bathrooms. Humidity above 60 percent fosters growth.
Health and fix
Mold can cause allergy symptoms and asthma flares. Fix leaks, run dehumidifiers, ventilate and clean with detergent. The EPA advises professional help for areas over about 10 square feet.
Typical locations
Musty odor appears in basements, closets, cars, laundry and rooms with leaks. Mold spores thrive at relative humidity above 60 percent and need moisture for 24 to 48 hours to start growing. Mildew produces microbial volatile organic compounds that smell earthy. Old books and stored fabrics hold odors.
Health and remedies
Mold exposure is associated with asthma and respiratory symptoms, as reported by the Institute of Medicine. Fix leaks, run dehumidifiers to hold 30 to 50 percent humidity, ventilate bathrooms and clean small mold areas (under 10 square feet) with detergent and water. Activated charcoal and baking soda absorb odor. Larger areas need professionals. Do not mix bleach with ammonia.
Based on data from the US Environmental Protection Agency and the CDC
