Mold and mildew are simple, microscopic organisms that can grow virtually anywhere if they have adequate moisture, nutrients and appropriate temperatures. Depending on the particular mold or mildew, growing colonies can be almost any color from white to black. Most household molds and mildews are black, grey or charcoal colored. Spores of dozens of kinds of mold and mildew are present at all times in indoor and outdoor air. These spores can settle, germinate and grow wherever good growth conditions are found. They can grow on soil, plants, dead plant materials, foods, fabrics, paper, wood and many other materials. Most molds are not harmful. In fact, molds have important roles in the environment and in living systems. In soil molds play a crucial part in decomposition of organic matter and in making nutrients available to plants.
Household mold or moldew should be a cause for concern. Mold and mildews are harmful at least to the materials on which they grow, and they usually produce objectionable, musty odors, stains, decomposition (rotting of materials), and discolorations. If mold conditions are allowed to exist for long in a wood structure, the wood can quickly become weak and rotten. Fabrics and paper can be seriously damaged or destroyed in days by damp, moldy conditions. If molds grow extensively, they may produce enough airborne irritants to cause coughing and cold-like symptoms. Allergic persons may react to very small amounts of mold.
Flooding, leaking water pipes or fixtures, backed-up or faulty drain plumbing, leaky roofs, use of humidifiers, extensive use of hot water indoors (laundering, cooking, bathing) without adequate exhaust venting for steam, damp basements or crawlspaces, houseplant water or aquarium leakage, indoor clothes drying, and unvented combustion appliances are all important sources of indoor moisture, and can encourage mold growth. Heavy condensation ("sweating") of windows, exterior walls or other cold objects indicates excessive moisture and inadequate venting.
Where colonies are extensive they can also produce enough spores, and by-products to be harmful to health. Many of the by-products of mold and mildew are irritating to skin, eyes and respiratory tracts. Some molds produce true allergic sensitization and allergic reactions in susceptible people. Some molds produce toxic by-products that could be harmful to skin, and poisonous if ingested or inhaled in quantity.
Generally it is not necessary or helpful to test molds found in homes. Usually damp areas in homes will have a large number of molds growing together. Even though many molds produce toxic or potentially toxic substances, merely finding such a mold in a home does not mean that the mold poses a serious or extreme hazard to people in the home. There is very little known about the health significance of most household molds. If one has a specific mold allergy and needs to know if that particular mold is present, then testing may be helpful. General tests to determine total numbers of molds or spores in air samples may be useful in determining if there is a significant but unidentified indoor source of mold. There are private testing firms that offer such evaluations commercially.
How can mold be safely removed?
When removing mold or handling moldy materials it is wise to avoid direct skin contact with the mold. Impervious gloves, long pants and long sleeves should be worn. It is best to handle moldy materials when they are damp. Dry materials release many more spores and small particles into the air. If the materials are dusty, it is advisable to wear a fabric or paper dust mask over the nose to filter out dust particles. Make sure the area where you are working is well ventilated. Moldy materials should be tied tightly in plastic bags and placed in the garbage before they dry out.