Mold in General:
Mold spores are found both indoors and outdoors. Mold spores cannot be completely eliminated from indoor environments. Some mold spores will be found floating through the air and on settled dust; however, they can only grow if moisture is present.
Mold is not usually a problem indoors-unless mold spores land on a wet or damp spot and begin growing. As molds grow, they digest whatever they are growing on. Unchecked mold growth can damage buildings and furnishings; molds can rot wood, damage drywall, and eventually cause structural damage to buildings. Mold can cause cosmetic damage, such as stains, on furnishings. The potential human health effects of mold are also a concern. It is important, therefore, to prevent mold from growing indoors.
Although the issue of whether exposure to indoor fungi causes adverse health effects is controversial, there is no doubt that a seriously mold-contaminated building can suffer structural damage, and that a foul-smelling, fungus-filled building is certainly aesthetically unpleasant. Controversies about health effects aside, the latter two reasons are sufficient to merit a Complete Mold Inspection and remediation when an environment is found to have fungal contamination.
People who have concerns about structural damage or the aesthetic effects of indoor fungi should seek the services of a licensed mold inspector. People who have concerns about health effects of mold exposure should seek the advice of a healthcare professional.
Fungi grow well in moist, dark areas, but can be found wherever organic material is available. Molds can grow on a variety of surfaces, including paint, jet fuel, wallpaper, glass and stainless steel. Moisture is necessary for mold growth. Moisture may come from the air and from the material upon which mold grows. If the environment becomes very dry, fungi can survive by going dormant or by producing spores that resist dry conditions.
Fungi can spread via tiny spores through the air. When a spore lands upon a surface that is moist and has material that can be used for food, it germinates and begins to grow. Hyphae grow out of the spores. Some of these grow up into the air. Spores are produced on the hyphae that grow upward, above the food material. Spores can then be blown around by the wind and spread to new areas.
Inhalation exposure to mold indoors can cause negative health effects in some people. Molds produce allergens (substances that can cause allergic reactions), irritants and, in some cases, potentially toxic substances (mycotoxins). Inhaling or touching mold or mold spores may cause allergic reactions in sensitive individuals. Mold does not have to be alive to cause an allergic reaction in some people.
There are some specific groups of people who are potentially more easily or severely affected by mold than the average individual with no sensitivities to mold. They include infants, children, elderly people, individuals with respiratory conditions (such as allergies and asthma), and people with weakened immune systems (people with HIV/AIDS, chemotherapy patients, and organ transplant recipients).
Sensitive people should avoid areas that are likely to have mold, such as compost piles, cut grass and wooded areas.
Allergic reactions to mold in buildings do occur for many sensitive people. However, there is no conclusive evidence that proves that mold in a building directly causes human illnesses. More research is needed, and mold research has been continuous.
Mold can be found in the air inside a building, on a surface inside a building (on the floor, ceiling, walls and furniture), and inside the HVAC system of a building. Many of these micro-organisms come indoors from outside. They come from decaying organic matter or moist earth.
Mold can enter a building by floating with outdoor air that enters the building, or they can travel on people and animals who bring them inside.
Mold might be present on the building materials as the structure is being constructed. Often, inspectors will find building materials lying on the ground at a new-construction site. These materials absorb moisture and dirt and may support mold growth inside the building, after construction has been completed.
Mold growth is not desirable in a building and must be prevented. There are three reasons to prevent fungal growth inside a building: the potential negative health effects of exposure to fungi and their byproducts; the effects of mold contamination on the structural integrity of the building; and the negative aesthetic effects fungi can produce both visually and on the human olfactory system.
Building science, in relation to mold, is the study of the building's dynamics as affected by moisture intrusion. Buildings are dynamic environments influenced by geographic location, season, weather conditions, HVAC system design and operation, moisture intrusion, pest colonization, and human activities. Building dynamics continually change and affect the conditions for mold growth.
Mold growth does not require the presence of standing water; it can occur when high relative humidity or the moisture retaining properties of building surfaces allow sufficient moisture to accumulate.
A building can become a perfect place for mold growth when the building has construction flaws, systems or components that are damaged or inoperable, or experience delayed maintenance. Any part of a building that facilitates moisture to enter into its materials creates the potential for mold growth. Wooden components, drywall, carpeting, plaster, wallpaper, and many other building materials provide fertile conditions for mold growth when they become wet. Water-damaged materials provide optimum sites for mold growth.
Just over a third of all homes in the United States experience some type of water damage every year. Where there is water damage, there may be mold growth. When a home has mold growth, addressing the problem can create an additional financial burden, not to mention potentially serious health risks.
Common moisture problems include:
• leaking roofs;
• leaking or condensation on water pipes, especially pipes inside wall cavities or pipe chases;
• leaking fire-protection sprinkler systems;
• landscaping, gutters and downspouts that direct water into or under a building;
• high humidity (greater than 60% relative humidity);
• unvented combustion appliances, such as clothes dryers vented into a garage (clothes dryers and other combustion appliances should be vented to the outdoors); and
• under-floor crawlspaces with exposed dirt floor.
Some moisture problems are not easy to see. For example, the interiors of walls where pipes and wires are run (pipe chases and utility tunnels) are common sites of mold growth. Mold is frequently found on walls in cold corners and behind furniture where condensation can form.
Other potential locations of hidden moisture, resulting in hidden mold growth, include:
• poorly draining condensate drain pans inside air-handling units;
• porous thermal or acoustic liners inside ductwork;
• roof materials above ceiling tiles;
• the backside of drywall (also known as gypsum board, wallboard, or Sheetrock®), or
• under carpeting and pads;
• behind wallpaper;
• under vinyl flooring;
• inside sink cabinets;
• under furniture; and
• behind stored items placed near an exterior wall or on a cold floor.
Preventing Mold Growth:
Keep the building and furnishings dry. When things get wet, dry them quickly (within 24 to 48 hours). Perform routine cleaning, maintenance and repairs. The key to mold prevention is moisture control. Water intrusion into buildings or a building's crawlspaces should be controlled. If water enters a building through a leaking roof or because of a flood or accident, it should be removed immediately and the affected areas should be dried out.
Special attention should be given to areas that are hidden, but that might have gotten wet. Areas behind walls and in ceilings, crawlspaces and attics are frequently overlooked and not dried carefully. In general, all wet areas should be completely dried within 48 hours to prevent mold from growing.
Routine Maintenance is Important
A number of items frequently subject to mold problems should be checked and maintained routinely. Furnace humidifiers must be cleaned regularly to prevent mold and bacterial growth. Ducts in which humidifiers are installed should also be checked to ensure that water has not leaked into the furnace or filter areas. Stand-alone humidifiers should be cleaned frequently to ensure that they are not moldy. Pay special attention to any filters in the humidifier because they can become moldy, and the humidifier can spread spores throughout the area. Carpeted areas around the humidifiers should also be monitored for wetness. Humidifiers should be set to produce less than 60% relative humidity in the building. Relative humidity greater than 60% is likely to result in condensation in the building, and that can lead to mold growth.
HVAC systems should be checked routinely because mold in a ventilation system may be spread throughout the building. Drain or condensate pans should also be checked regularly because they can become reservoirs for mold and bacteria if they are not installed and maintained properly. These pans are designed to remove water produced by cooling hot air from the ventilation system. If the pans do not drain, or are not cleaned frequently, they may allow water to enter the HVAC system and contaminate the ventilation ducts in the building. The pans themselves may grow mold and allow mold spores to be spread throughout the building. Filters for the HVAC system should be kept dry and should be changed frequently.
Toilet and bathroom areas should be carefully monitored for water and plumbing leaks. Rippling wall coverings, cracked drywall tape, peeling paint, and other signs of water damage should be investigated immediately. Such signs often indicate that water has leaked somewhere, and hidden mold growth and damage are likely. Water seepage into crawlspaces and basements should also be stopped quickly to ensure that mold will not grow. Additional measures, such as installing sump pumps and/or re-grading the area around the building, should be considered to prevent future leaks. Any areas that smell moldy or musty should be investigated to ensure that water has not entered and that mold is not growing.
Mold Prevention Tips
• Moisture control is the key.
• Keep the building clean and dry. Dry any wet or damp areas within 48 hours.
• Fix leaky plumbing and any leaks in the building's envelope as soon as possible.
• Watch for condensation and wet spots. Fix the sources of moisture problems as soon as
• Prevent moisture due to condensation by increasing surface temperature or reducing the
moisture level in the air (humidity). To increase surface temperature, insulate or increase air
circulation. To reduce the moisture level in the air, repair leaks and increase ventilation (if
outside air is cold and dry), or dehumidify (if outdoor air is warm and humid).
• Keep heating, ventilation and air conditioning (HVAC) drip pans clean, flowing properly, and
• Vent moisture-generating appliances, such as dryers, to the outside, where possible.
• Maintain low indoor humidity, below 60% relative humidity (RH), and, ideally, between
30% and 50%, if possible.
• Perform regular building and HVAC inspections and scheduled maintenance.
• Don't let foundations stay wet. Provide drainage, and slope the ground away from the
• If you are not experienced with home and building repairs, you may want to consult a
professional when making necessary repairs, or for assistance related to mold-prevention
changes to your home or building.