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Indoor Moisture

This fact sheet provides information on how to identify potential indoor moisture problems in the home and ways to correct them.

How can moisture in my home affect my health?

If you have a moisture problem that is not addressed, it can lead to mold growth, pests (i.e., cockroaches, mice) and structural damage. These conditions may lead to health symptoms such as:

  • Irritation of eyes and throat
  • Runny nose or nasal congestion
  • Worsening of existing asthma or other breathing problems

If you experience any of these symptoms, please contact your healthcare provider. Keep in mind that symptoms associated with indoor moisture problems can also be caused by many other illnesses.

What are the first signs of an indoor moisture problem in my home?

The following conditions indicate a moisture problem inside the home:

  • Water leaks and stains on walls
  • A musty, earthy or stale odor
  • Water or dampness on windows and
    other cool surfaces
  • Swollen or warped walls or floors
  • Mold and mildew growth
  • Peeling or bubbling paint

If you notice any of these signs in your home, find the source of the moisture and repair it. If you are a tenant, talk to your building owner or manager about repairing the problem. Fix these problems as soon as possible to help reduce the amount of moisture in your home.

What causes indoor moisture?

Many things can increase moisture inside the home, including:

  • Leaky roofs, windows and pipes
  • Floods or sewer backups
  • High indoor humidity
    (a relative humidity level between 40-60% is best)
  • Improperly vented clothes dryers
  • Gutters that drain too close to the home
  • Improperly used humidifiers
  • Water build-up around the base of the building
  • Cooking without proper ventilation
  • Faulty air conditioning
  • Showering without proper ventilation
What can I do to prevent indoor moisture?

The following basic steps can help to keep you and your family healthy and protect your home:

  • Ventilate areas that get wet and damp, such as bathrooms, kitchens, basements or crawlspaces. Open windows or use exhaust fans that vent to the outside.
  • Control humidity levels in your home. Maintain good ventilation to reduce humid conditions indoors. A dehumidifier or an air conditioner may also help lower humidity levels. A relative humidity level between 40 – 60% is best. You can monitor humidity levels with a humidity detector, which you can buy from a hardware store.
  • If you own your home, check the outside of the home for any leaks or cracks that water can enter. Fix any leaks in the roof, walls, or plumbing promptly. Also, check gutters and down spouts to make sure that they are functioning properly, and check that water drains away from your home and not towards it.
  • If you rent or live in a multi-unit building, talk to the owner/building manager about fixing the leaks and cracks inside your home. If the problem is not fixed, call 311.
  • If you have mold or mildew in your home, please visit NYC Health - Mold for more information on how to safely clean and prevent it.
  • Vent moisture-generating appliances, such as dryers, to the outside.
  • When cooking, use kitchen range hoods and exhaust fans, or open windows to let in fresh air.
  • If you have experienced flooding, clean and dry out your home as quickly as possible. For more information on cleanup after floods, please visit NYC Health - Floods.

When improving or rebuilding homes, owners can:

  • Use building materials that retard mold growth if available.
  • Install double-glazed windows to reduce condensation.
  • Ventilate crawl spaces to prevent moisture build-up.
  • Install range hoods that vent to outside and window fans in the kitchen.
  • Avoid using carpets in rooms or areas like bathrooms or basements that may have a lot of moisture.
Additional Information

For more information on indoor air quality and other relevant topics, visit: