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Indoor Air Quality

Poor Indoor Air Quality: Dampness and Mold

The link between dampness and respiratory problems is well established.1 Multiple studies have shown that dampness and mold (fungi) are associated with asthma diagnosis, asthma symptoms, colds, nasal symptoms, and eczema. Recently, several studies have shown that indoor dampness actually causes asthma attacks in children with asthma.2 Adults living in damp homes also have more asthma attacks.

There are many reasons why dampness can cause breathing problems. Moisture can lead to the growth of mold indoors.3 Dust mites are common in humid environments. Damp environments may have more allergenic bacteria. Moisture may cause carpeting and vinyl flooring to release irritating chemicals.2 Standing water attracts cockroaches. It can be difficult to tell which allergen or irritant is causing asthma symptoms.

How common are mold and mold allergy?

About 10% of the population is allergic to mold, and about 5% have allergic symptoms.4 Dampness and mold are found in 18% to 50% of buildings.1 Visible mold and dampness, a musty odor, and water damage indicate water problems in the home.2 Common causes of water problems in the home are leaks, condensation, damp crawl spaces and basements, inadequate ventilation, and plumbing problems, as well as bathing and cooking.5

What can I do to improve indoor air quality?

It is necessary to clean and remove moldy items. To prevent the mold from returning, you will need to fix the water or moisture problem. One study showed that people who treated visible mold had fewer asthma symptoms and needed less asthma medication.6

Tips for removing mold:

  • Clean visible mold with detergent and water. Dry the surface thoroughly. To limit your exposure to mold, wear an N-95 respirator, gloves, and goggles when cleaning.7
  • Remove moldy items, such as carpets and ceiling tiles.2,7 Mold can hide in the spaces and crevices of porous materials, making them impossible to clean.
  • Consider applying a fungicide to moldy areas.5 You may need the help of a professional for this step.
  • Clean bathrooms frequently to limit the growth of mold.7

Tips for reducing moisture in your house:

  • Fix leaks.2
  • Address plumbing problems quickly.7
  • Use a dehumidifier.7 Whole house dehumidifiers can be installed. Alternatively, you can use a dehumidifier in damp areas, such as the basement.3 Humidity should be kept below 60%, although 30% to 50% is even better.3 Humidity meters can be purchased in hardware stores.
  • Use an air conditioner in warm and humid environments.5
  • Do not use swamp (evaporative) coolers or humidifiers.3
  • Clean and repair roof gutters regularly.7
  • Install and use ventilation fans in damp rooms, such as bathrooms, the kitchen, or laundry room.5
  • Open window to increase ventilation in damp rooms.7
  • Make sure the ground slopes away from your house to keep water from entering the foundation.7
  • Keep air conditioner drip pans clean and drain lines clear.8

Mold occurs naturally outdoors, helping to break down leaves and wood. When there are high levels of mold and pollen outside, keep windows and doors shut. This step can keep outdoor allergens from affecting the air quality inside your house.8

Written by: Sarah O'Brien | Last Reviewed: May 2016.
  1. Mendell MJ, Mirer AG, Cheung K, et al. Respiratory and allergic health effects of dampness, mold, and dampness-related agents: a review of the epidemiologic evidence. Environ Health Perspect. 2011;119:748-756.
  2. Kanchongkittiphon W, Mendell MJ, Gaffin JM, Wang G, Phipatanakul W. Indoor environmental exposures and exacerbation of asthma: An update to the 2000 review by the Institute of Medicine. Environ Health Perspect. 2014 Oct 10.
  3. National Heart, Lung, and Blood Institute. Expert panel report 3 (EPR-3): Guidelines for the diagnosis and management of asthma - Full Report 2007. Accessed 11/12/14 at:
  4. Bush RK, Portnoy JM, Saxon A, Terr AI, Wood RA. The medical effects of mold exposure. J Allergy Clin Immunol. 2006;117:326-333.
  5. Krieger J, Jacobs DE, Ashley PJ, et al. Housing interventions and control of asthma-related indoor biologic agents: a review of the evidence. J Public Health Manag Pract. 2010;16(5 Suppl):S11-S20.
  6. Burr ML, Matthews IP, Arthur RA, et al. Effects on patients with asthma of eradicating visible indoor mould: a randomized controlled trial. Thorax. 2007;62:767-772.
  7. Environmental Protection Agency. A brief guide to mold, moisture, and your home. Accessed 1/9/15 at:
  8. Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention 2014. Accessed 11/12/14 at: