Mold (and mildew) are common terms for fungi that can grow in damp locations in buildings, although molds are present everywhere, indoors and outdoors. Molds are important microorganisms because they help break down dead plant and animal material and recycle nutrients in the environment. There are many kinds of molds, and mold growth can have many forms and colors. To grow and reproduce, mold only needs food — any organic matter, such as leaves, wood, paper, or even dust — and moisture. Organic matter is almost always available, so whether mold grows depends mostly on whether there is moisture. By fixing moisture problems, you can keep mold from growing in your home.

The presence of visible mold, visible moisture, water-damaged materials, or mold odor in a building is clearly linked to increased risk of various respiratory health effects. These health effects include asthma development, asthma exacerbation, allergies, respiratory infections, and a variety of upper and lower respiratory symptoms. The more extensive or severe the dampness and mold, the greater the risk of health effects. The health effects also depend on the susceptibility of the occupants. Speak to your doctor if you have concerns about the health effects of mold.

A doctor can test for and diagnose a small number of mold allergies. However, a person may have mold allergies for which there is no test. Also, molds can have health effects other than allergic reactions and can affect people who are not allergic. Still, it is a good idea to discuss your concerns with your healtcare provider.

No. Any type of mold that you see or smell in your building is a risk to your health and should be fixed. The more mold or moisture that you see or smell, the greater the risk to your health. There is currently no evidence that the particular kind of mold in your building matters.

Mold or moisture problems may be visible or hidden. Visible areas could include surfaces in the building itself and items in the building. Examples of hidden problem areas include beneath wallpaper, behind furniture, behind baseboards, or inside walls, floors, or ceilings. Signs of a mold or moisture problem in your home are: Water-stained, discolored, or moldy surfaces Water damage, such as warped floors, peeling or bubbled paint, or rotting wood Damp surfaces, including condensation on windows or walls An earthy, musty, or moldy smell You might also have a mold problem if people who are sensitive or allergic to mold have symptoms when they are in your home.

There are several steps to fixing a mold or dampness problem. Find the damp or moldy areas Fix the source of the moisture problems Dry or replace wet materials Clean or remove moldy materials

Excess moisture can come from either indoor or outdoor sources. Indoor sources include: Leaking or burst pipes Insufficient venting where water is used (for example, bathrooms, laundry areas, and kitchens) Condensation on cold surfaces Outdoor sources include: Water intrusion (leaky roofs, leaky windows) and flooding Outdoor surfaces that slope and drain water toward the home Sprinklers and downspouts directing water at the house

You are right not to ignore mold odor, because this is one of the best indicators of potential health risks from dampness or mold. If you cannot find the mold or moisture problem, you may need a general contractor experienced with water damage assessment to find the source of the mold odor. Thorough mold investigations may require some damage to building materials to find mold or dampness in hidden spaces. We do not recommend testing for mold.

Generally, materials are either porous or non-porous. Non-porous materials (such as glass, plastic, metal, or ceramics) do not absorb water and can be effectively cleaned of mold [see next question]. Porous materials (such as drywall, ceiling tiles, drapes, or upholstered furniture) do absorb water and usually cannot be effectively cleaned of mold. If the porous materials look or smell moldy, they should be removed. In addition, porous materials that have stayed wet for more than a day or two may need to be removed, even if they do not yet look or smell moldy, because mold may have started to grow under some conditions.

If you are sensitive to mold or if the amount of mold is large, consider having another person or professional do the work. Use personal protective equipment, such as goggles, gloves, and an N-95 particulate respirator. A "dust mask" will not protect you from mold. It is also advisable to wear removable protective clothing (such as disposable suits) while handling moldy material, as mold can collect on clothes and be released later. It is important to prevent contamination from spreading from the source area to other areas in the home [see guidelines below]. It is also a good idea to ventilate the area you are cleaning to the outdoors during and after the work. Cleaning non-porous materials: Scrub non-porous materials thoroughly with soap and water to remove mold. We do not recommend using bleach or products that contain bleach. Bleach can be a respiratory hazard and disinfection is not necessary if you have cleaned the material thoroughly with soap. Removing porous materials: Moldy materials should be sealed in disposable bags or wrapped in plastic and disposed of as normal trash. The moldy material does not need to be treated as hazardous waste.

Painting over mold, even after applying a biocide, will not fix mold and dampness problems. Removing damaged materials, but not addressing the underlying moisture problem, is also ineffective. Running particle-removing air filters or air cleaners will not solve a mold problem.

Removing moldy materials can raise mold levels in the air, so it’s advisable for unprotected persons to avoid exposures during remediation. During and after remediation, precautions should be taken to prevent mold spores from contaminating other areas on the home. Containment of the remediation area and the moldy materials, including sealing vents to heating/air conditioning/ventilation systems, followed by cleanup are important safety measures. In larger remediation projects, containment may require sheeting and maintaining negative pressure in the containment area.

The best known indicator that the dampness-related health risks have been reduced is if the source of the moisture is remedied, all damaged materials have been cleaned or removed appropriately, and all remaining materials are dry and free of visible mold and mold odor. As of now, no mold tests or measurements can show when remediation efforts have been successful.

Correcting the moisture problems and preventing or quickly responding to future moisture problems will keep mold from growing indoors. Also, porous materials that were previously moldy but not removed will be even more susceptible to mold regrowth.