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Dampness and Mold in Buildings

Water damaged ceiling tiles  Mold on ceiling tile

Dampness results from water incursion either from internal sources (e.g. leaking pipes) or external sources (e.g. rainwater). Dampness becomes a problem when various materials in buildings (e.g., rugs, walls, ceiling tiles) become wet for extended periods of time. Excessive moisture in the air (i.e., high relative humidity) that is not properly controlled with air conditioning can also lead to excessive dampness. Flooding causes dampness. Dampness is a problem in buildings because it provides the moisture that supports the growth of bacteria, fungi (i.e., mold), and insects.

In the presence of damp building materials the source of water incursion is often readily apparent (e.g., leaks in the roof or windows or a burst pipe). However, dampness problems can be less obvious when the affected materials and water source are hidden from view (e.g., wet insulation within a ceiling or wall; excessive moisture in the building foundation due to the slope of the surrounding land).


NIOSH Alert: Preventing Occupational Respiratory Disease from Exposures Caused by Dampness in Office Buildings, Schools, and Other Nonindustrial Buildings

cover of 2013-102

Office buildings, schools, and other nonindustrial buildings may develop moisture and dampness problems from roof and window leaks, high indoor humidity, and flooding events, among other things. For this Alert, we define "dampness" as the presence of unwanted and excessive moisture in buildings [AIHA 2008]. This can lead to the growth of mold, fungi, and bacteria; the release of volatile organic compounds; and the breakdown of building materials. We use the term "mold" for a group of fungi that are common on wet materials. Outdoors, molds live in the soil, on plants, and on dead or decaying matter. There are thousands of species of molds and they can be any color. Different mold species can adapt to different moisture conditions. Research studies have shown that exposures to building dampness and mold have been associated with respiratory symptoms, asthma, hypersensitivity pneumonitis, rhinosinusitis, bronchitis, and respiratory infections. Individuals with asthma or hypersensitivity pneumonitis may be at risk for progression to more severe disease if the relationship between illness and exposure to the damp building is not recognized and exposures continue.

NIOSH Alert: Preventing Occupational Respiratory Disease from Exposures Caused by Dampness in Office Buildings, Schools, and Other Nonindustrial Buildings
DHHS (NIOSH) Publication No. 2013-102 (November 2012)

What is mold?

Mold is a fungal growth that forms and spreads on various kinds of damp or decaying organic matter. There are many different mold species that come in many different colors. Molds are sometimes referred to as mildew. They are found both indoors and outdoors in all climates, during all seasons of the year. Outdoors, molds survive by using plants and decaying organic matter such as fallen leaves as a source of nutrition. Indoors, molds need moisture to grow as well as a carbon source from building materials or building contents.

Excess moisture is generally the cause of indoor mold growth. Molds reproduce by releasing tiny spores that float through the air until landing in other locations. When they settle on wet or moist surfaces, the spores can form new mold colonies. Moderate temperatures and available nutrient sources make most office buildings ideal for mold growth.

Recent media attention has increased public awareness and concern over exposure to molds in the workplace. While this may seem to be a new problem, exposure to molds has actually occurred throughout history. In fact, the types of molds found in office buildings are not rare or even unusual. It is important to understand that no indoor space is completely free from mold spores – not even a surgical operating room. Molds are everywhere, making our exposure to molds unavoidable, whether indoors or outdoors, at home or at work.

Collage: old leaking pipe and mold on stairs/floor

"Toxic Mold" & Stachybotrys chartarum

Certain molds are toxigenic, meaning they can produce toxins (mycotoxins), but the molds themselves are not toxic, or poisonous. Hazards presented by molds that may produce mycotoxins, such as Stachybotrys chartarum, should be considered the same as other common molds which can grow in your house or workplace. Contradicting research results exist regarding whether toxigenic mold found indoors causes unique or rare health conditions such as bleeding in the lungs. Research is ongoing in this area.

Mold growing in buildings, whether it is Stachybotrys chartarum (Stachybotrys atra) or another mold, indicates that there is a problem with water or moisture. This is the first problem that needs to be addressed. For further information on Stachybotrys chartarum, go to the

CDC mold website

Remediation of dampness and mold contamination

First and foremost, determine the source of moisture and take appropriate measures to make repairs. Damp or wet building materials and furnishings as a result of leaks or flooding should be dried within 24 to 48 hours to prevent the growth of mold. Mold can be cleaned and removed from hard surfaces with detergent and water or a bleach solution of no more than 1 cup of bleach in 1 gallon of water. Never mix bleach with ammonia or other household cleaners. Mold in or under carpets typically requires that the carpets be removed. Once mold starts to grow in insulation or wallboard, the only way to deal with the problem is removal and replacement. For complete remediation guidelines go to the New York City Department of Health and Hygiene's Guidelines on Assessment and Remediation of Fungi in Indoor Environments site.

I suspect mold in my workplace. How do I test for mold?

CDC does not recommend routine sampling for molds. Generally, it is not necessary to identify the species of mold growing in a building. Measurements of mold in air are not reliable or representative. If mold is seen or smelled, there is a potential health risk; therefore, no matter what type of mold is present, you should arrange for its removal. Furthermore, sampling for mold can be expensive, and standards for judging what is and what is not an acceptable or tolerable quantity of mold have not been established.

Symptoms related to dampness and mold

A woman sneezing into a tissue.

Health problems associated with excessive damp conditions and mold include:


    Allergic responses like those to pollen or animal dander are the most common types of health problems related to mold. Typical symptoms include sneezing; irritation of the nose, mouth, or throat; nasal stuffiness and runny nose; and red, itchy or watery eyes. Inhaling or touching mold or mold spores can cause a person who was not previously allergic to mold to become allergic to mold. For people with known allergies, molds can trigger asthma symptoms such as shortness of breath, wheezing, or cough. Irritation can also occur in non-allergenic (non-sensitized) people. Additionally, scientific studies indicate that exposure to molds in the workplace can make pre-existing asthma worse. Recent NIOSH investigations document that some damp buildings are associated with developing new asthma.


    Hypersensitivity pneumonitis (HP) is a kind of lung inflammation that occurs in persons who develop immune system sensitization (similar to an allergy) to inhaled organic dust. It can be mistaken for pneumonia, but it does not get better with antibiotics for infection.

    Symptoms of HP can vary. Some persons have shortness of breath, cough, muscle aches, chills, fever, night sweats, and profound fatigue. These symptoms usually first appear 2 to 9 hours after exposure and last for 1 to 3 days. Other affected persons have progressive shortness of breath and cough, as well as weight loss. Work-relatedness may only become apparent over long holidays if symptoms resolve and then recur on return to work. With continued exposure, the persistent lung inflammation of both kinds of symptoms can lead to scarring and permanent damage. The slow progression of symptoms and the persistence of symptoms away from work may result in delayed recognition of work-related lung disease by both workers and physicians.

    HP has been referred to as Bird breeder’s lung and Mushroom picker’s disease in specific occupations with a risk of HP from biological dusts. HP has been documented in workers in buildings with mold and bacteria contaminated air-conditioners (including spray-water cooling systems), and contaminated ductwork and filters. This lung disease has also occurred in workers who worked in water-damaged buildings with roof leaks, plumbing leaks, poorly draining condensation pans, and high indoor relative humidity.

    HP is not contagious and is due to a person’s immune system reaction to inhaled microorganisms, whether dead or alive. It is possible for workers to have both dampness-related HP and asthma at the same time. Additionally, workplaces that have workers with HP may also have workers with building-related asthma.


    Asthma is a form of lung disease in which the airways develop inflammation and bronchospasm (reversible narrowing) in response to sensitizing or irritating exposure. Affected individuals can experience episodes of shortness of breath, cough, chest tightness, and wheezing. These symptoms occur after exposure to nonspecific irritating substances in the air or after exposure to substances to which an individual is allergic. Medical testing typically reveals evidence of bronchial hyperresponsiveness such as an abnormal methacholine challenge test or reversible airways obstruction on spirometry (a test of lung function). It is important for affected individuals to have a comprehensive asthma treatment plan and regular follow-up with their physician. Early diagnosis and removal from the impacted damp office environment can cure asthma caused by workplace exposures.

    In approximately 15% of asthmatics, the illness may have been caused, or made worse, by workplace exposures. Some occupational exposures are well known risks for asthma development (e.g., western red cedar; isocyanates). Indoor environment research has identified evidence of an association between damp buildings and asthma symptoms in individuals with pre-existing asthma. There is also new evidence of an association between damp buildings and new-onset asthma. In an individual with new-onset asthma or worsening of stable pre-existing asthma, measurements of lung function made several times a day at work and at home over several weeks may reveal a pattern of changing lung function that suggests a workplace cause.

    For individuals with new-onset asthma or worsening of stable pre-existing asthma that is suspected to be related to the indoor environment, controlling or eliminating the sources of indoor contaminants, along with optimal medical treatment, may lead to symptoms of improvement or resolution.

What workers can do

When workers suspect their health problems are caused by exposure to building-related dampness or mold, workers should:

  • Report concerns immediately to supervisors or those persons responsible for building maintenance.
  • See your doctor for proper diagnosis and treatment.
  • Ask your doctor whether you should be medically restricted from the affected environment.

What management and building owners can do

When health problems are believed to be caused by exposure to dampness or mold in the workplace, owners and managers should:

  • Always respond when occupant health concerns are reported.
  • Establish clear procedures for recording and responding to IEQ complaints to ensure an adequate and timely response.
    • Log all complaints or problem reports.
    • Collect information about each complaint.
    • Ensure confidentiality.
    • Determine a plan for response.
    • Identify appropriate resources for response.
    • Apply remedial action.
    • Provide feedback to building occupants regarding the complaint and response actions.
    • Follow-up to ensure that remedial action has been effective.
  • Regularly inspect building areas for evidence of dampness; take prompt steps to identify and correct the causes of any dampness problems found.
  • Conduct regularly scheduled heating, ventilating, and air-conditioning (HVAC) system inspections, and promptly correct any problems.
  • Prevent high indoor humidity through the proper design and operation of HVAC systems.
  • Dry any porous building materials that have become wet from leaks or flooding within 48 hours.
  • Encourage occupants who have developed persistent or worsening respiratory symptoms while working in the building to see a health care provider.
  • Follow health care provider recommendations for relocation of occupants diagnosed with building-related respiratory disease.
  • Establish an indoor environmental quality (IEQ) team consisting of a coordinator and representatives of the building employees, employers, and building management who would oversee implementation of an IEQ program. The EPA Indoor Air Quality Tools for Schools can be used as a model for such a program.

Dampness and Mold Assessment Tool

Screen capture from Dampness and Mold Assessment Tool

NIOSH has developed an observational assessment tool for dampness and mold in buildings. The tool is currently in review to become an official NIOSH document. The goal of the tool is to provide valuable information for motivating remediation, prioritizing intervention, and evaluating remediation effectiveness.

The tool consists of:

  1. A form that is used to evaluate signs of dampness, water damage, mold growth, and musty odors in rooms and areas throughout a building.
  2. A Visual Basic© data entry application to enter data collected from hard copy evaluation forms for electronic record keeping and reports. Data is stored in a Microsoft Access© database. The software may also be implemented on PC-based tablets. The software is still under development. Once completed, the software will be made available at this website.

Screen capture from Dampness and Mold Assessment Tool

For additional information or to receive a form and instructions for use, contact us at

Related Resources

American Industrial Hygiene Association (AIHA) - Facts about Mold

AIHA - Position Statement on Mold and Dampness in the Built Environment

ASHRAE - Limiting Indoor Mold and Dampness in Buildings

Centers for Disease Control and Prevention (CDC) - Mold

CDC - Facts about Mold and Dampness

Department of Health and Human Services, National Toxicology Program: Fact Sheet on Mold

The Environmental Law Institute (ELI) - State-based laws and regulations

ELI - Topics in School Environmental Health

Environmental Protection Agency (EPA) - Guidance for Clinicians on the Recognition and Management of Health Effects Related to Mold Exposure and Moisture Indoors

EPA - Indoor Air Quality Design Tools for Schools

EPA - Mold and Moisture

EPA - Mold Remediation in Schools and Commercial Buildings

EPA - Mold Resources

Institute of Medicine of The National Academies - Damp Indoor Spaces and Health

Lawrence Berkley National Laboratory - Indoor Air Quality Scientific Findings Resource Bank - Indoor Dampness, Biological Contaminants, and Health

New York City Department of Health and Mental Hygiene - New York City Guidelines on Assessment and Remediation of Fungi in Indoor Environments

Occupational Safety and Health Administration (OSHA) - Mold

World Health Organization - Guidelines for Indoor Air Quality: Dampness and Mould