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Mold remediation |
This article is about mold growth in buildings, how to kill mold, and the more formal topics of assessment and remediation.
Mold assessment and Mold remediation are techniques used in occupational health: mold assessment is the process of identifying the location and extent of the mold hazard in a structure, and mold remediation is the process of removal and/or cleanup of mold from an indoor environment.
It has been estimated that 40 percent of United States homes have some form of mold problem.1
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Molds are ubiquitous in nature, and mold spores are a common component of household and workplace dust. However, when mold spores are present in large quantities, they can present a health hazard to humans, potentially causing allergic reactions and respiratory problems.
Some molds also produce mycotoxins that can pose serious health risks to humans and animals. Exposure to high levels of mycotoxins can lead to neurological problems and in some cases death. Prolonged exposure, e.g. daily workplace exposure, can be particularly harmful. The term toxic mold refers to molds that produce mycotoxins, such as Stachybotrys chartarum, and not to all molds in general.
Molds and fungi are found everywhere inside and outside, and can grow on almost any substance when moisture is present. Molds when they reproduce make spores, which can be carried by air currents. When these spores land on a moist surface that is suitable for life, they begin to grow. Molds are essential to the natural breakdown of organic materials in the environment. Mold is normally found indoors at levels that do not affect most healthy individuals. When these levels become abnormally high as determined by indoor air quality testing or a mold inspection, remediation is recommended to be carried out by a professional remediation company.citation needed
Because common building materials are capable of sustaining mold growth, and mold spores are ubiquitous, mold growth in an indoor environment is typically related to an indoor water or moisture problem. Mold growth may also be caused by incomplete drying of flooring materials such as concrete.2 Leaky roofs, building maintenance problems, or indoor plumbing problems can lead to mold growth inside homes, schools, or office buildings. Another common source of mold growth is flooding.
For significant mold growth to occur, there must be a source of water (which could be invisible humidity), a source of food, and a substrate capable of sustaining growth. Common building materials, such as plywood, drywall, furring strips, carpets, and carpet padding are food for molds. In carpet, invisible dust and cellulose are the food sources (see also dust mites). After a single incident of water damage occurs in a building, molds grow inside walls and then become dormant until a subsequent incident of high humidity; this illustrates how mold can appear to be a sudden problem, long after a previous flood or water incident that did not produce a mold-related problem. The right conditions re-activate mold. Studies also show that mycotoxin levels are perceptibly higher in buildings that have once had a water incident (source CMHC).
Both our indoor and outdoor environment have mold spores present. There is no such thing as a mold free environment in the Earth's biosphere.
Spores need three things to grow into mold:
Mold colonies can grow inside building structures. The main problem with the presence of mold in buildings is the inhalation of mycotoxins. Molds may produce an identifiable smell. Growth is fostered by moisture. After a flood or major leak, mycotoxin levels are higher in the building even after it has dried out (source: CMHC).
Food sources for molds in buildings include cellulose-based materials, such as wood, cardboard, and the paper facing on both sides of drywall, and all other kinds of organic matter, such as soap, dust and fabrics. Carpet contains dust made of organic matter such as skin cells. If a house has mold, the moisture may be from the basement or crawl space, a leaking roof, or a leak in plumbing pipes behind the walls. Insufficient ventilation can further enable moisture build-up. The more people in a space, the more humidity builds up. This is from normal breathing and perspiring. Visible mold colonies may form where ventilation is poorest, and on perimeter walls, because they are coolest, thus closest to the dew point.
If there are mold problems in a house only during certain times of the year, then it is probably either too air-tight, or too drafty. Mold problems occur in airtight homes more frequently in the warmer months (when humidity reaches high levels inside the house, and moisture is trapped), and occur in drafty homes more frequently in the colder months (when warm air escapes from the living area into unconditioned space, and condenses). If a house is artificially humidified during the winter, this can create conditions favorable to mold. Moving air may prevent mold from growing since it has the same desiccating effect as lowering humidity. Keeping indoor air temperature higher than 74 °F (23.3 °C) also has an inhibiting effect on mold growth.
Because common building materials are capable of sustaining mold growth, and mold spores are ubiquitous, mold growth in an indoor environment is typically related to an indoor water or moisture problem. Leaky roofs, building maintenance problems, or indoor plumbing problems can lead to mold growth inside homes, schools, or office buildings. Another common cause of mold growth is flooding.
Removing one of the three requirements for mold reduces or eliminates the new growth of mold. These three requirements are 1) Moisture, 2) Food source for the mold spores (dust, dander, etc), and 3) Warmth (mold generally does not grow in cold environments).
HVAC systems can create all three requirements for significant mold growth. The A/C system creates a difference in temperature that allows/causes condensation to occur. The high rate of dusty air movement through an HVAC system may create ample sources of food sources for the mold. And finally, since the A/C system is not always running - the ability for warm conditions to exist on a regular basis allows for the final component for active mold growth.
Because the HVAC system circulates air contaminated with mold spores and sometimes toxins - it is vital to prevent any three of the environments required for mold growth. A) Highly effective return air filtration systems are available that eliminate up to 99.9% of dust accumulation (as compared to 5% elimination by typical HVAC air filters). These newer filtration systems usually require modification to existing HVAC systems to allow for the larger size of electrostatic 99.9% filters. However, thorough cleaning of the HVAC system is required before usage of high efficiency filtration systems will help. Once mold is established - the mold growth and dust accumulation must be removed. B) Insulation of supply air ducts helps to reduce or eliminate the condensation that ultimately creates the moisture required for mold growth. This insulation should be place externally on the air ducts, because internal insulation provides a dust capture and breeding ground for mold.
The first step in an assessment is to determine if mold is present. This is done by visually examining the premises. If mold is growing and visible this helps determine the level of remediation that is necessary. If mold is actively growing and is visibly confirmed the need for sampling for specific species of mold is unnecessary.3
Another assessment method is to determine if the premise smells of mold, often described as an earthy or musty odor. However, not all molds produce the telltale mold odors.
These methods are considered to be non-intrusive and only visible and odor causing molds will be found. Sometimes more intrusive methods are needed to assess the level of mold contamination. This would include moving furniture, lifting and/or removing carpets, checking behind wallpaper or paneling, checking in ventilation duct work, opening and exposing wall cavities, etc.
Careful detailed visual inspection and recognition of moldy odors should be used to find problems needing correction. Efforts should focus on areas where there are signs of liquid moisture or water vapor (humidity) or where moisture problems are suspected. The investigation goals should be to locate indoor mold growth to determine how to correct the moisture problem and remove contamination safely and effectively.
The basic goals of any mold investigation are always twofold: 1) find the locations of mold growth, and 2) determine the sources of the moisture. If these can be answered by simpler or more cost-effective methods, mold testing is probably not a wise use of resources.
Many organizations exist that provide certification for mold investigation/assessments. However, only the American Indoor Air Quality Council provides accredited certifications. In the state of Texas there is legislation dictating who can and cannot perform investigation.citation needed
In general the EPA does not recommend sampling unless an occupant of the space is symptomatic. When sampling is necessary it should be performed by a trained professional who has specific experience in designing mold-sampling protocols, sampling methods, and the interpretation of findings. Sampling should only be conducted to answer a pertinent question: examples "what is the spore concentration in the air"," or is a particular species of fungi present in the building." The additional question should be asked before sampling "what action can or should a person take upon obtaining data."
The sampling and analysis should follow the recommendations of Occupational Safety and Health Administration (OSHA), National Institute for Occupational Safety and Health (NIOSH), Environmental Protection Agency (EPA), and the American Industrial Hygiene Association (AIHA). Most importantly, when a sample is taken the proper chain of custody should be adhered to. The AIHA offers lists of accredited laboratories that submit to required quarterly proficiency testing.
Three types of air sampling include but are not limited to:
When sampling is conducted, all three types is recommended by the AIHA, as each sample method alone has specific limitations. For example, air samples will not provide proof a hidden source of mold. Nor would a swab sample provide the level of contamination in the air.1
Though it may not be recommended, air sampling following mold remediation is usually the best way to ascertain efficacy of remediation, when conduct by a qualified third party.4
The first step in solving an indoor mold problem is stopping the source of moisture. Next is to remove the mold growth. Common remedies for small occurrences of mold include:
Significant mold growth may require professional mold remediation and removal of affected building materials. A conservative strategy is to discard any building materials saturated by the water intrusion or having visible mold growth.
There are many ways to prevent mold growth; see ventilation issues in houses.
In extreme cases of mold growth in buildings, it may be easier to condemn the building rather than clean the mold to safe levels.
Certain contractors are capable of repairing mold damage - usually by removing the affected areas and eliminating the cause of the excess moisture.
There are also cleaning companies that specialize in fabric restoration - a process by which mold and mold spores are removed from clothing to eliminate odor and prevent further mold growth and damage to the garments.
Improper methods for cleaning mold include exposure to high heat, dry air, sunlight (particularly UV light), ozone, and application of fungicides. These methods may render the mold non-viable, however, the mold and its by-products can still elicit health effects. As noted in following sections, the only proper way to clean mold is to use detergent solutions that physically remove mold. Many commercially available detergents marketed for mold clean-up also include an anti-fungal agent. The most effective way at this point is formal Mold Remediation.
The goal of remediation is to remove or clean contaminated materials in a way that prevents the emission of fungi and dust contaminated with fungi from leaving a work area and entering an occupied or non-abatement area, while protecting the health of workers performing the abatement. 5
The purpose of the clean-up process is to eliminate the mold and fungal growth and to remove contaminated materials. As a general rule, simply killing the mold with a biocide is not enough. The mold must be removed since the chemicals and proteins, which cause a reaction in humans, are still present even in dead mold.
Wet vacuum cleaners are designed to remove water from floors, carpets and other hard surfaces where water has accumulated. Wet vacuuming should only be used on wet materials, as spores may be exhausted into the indoor environment if insufficient liquid is present. After use this equipment must be thoroughly cleaned and dried as spores can adhere to the inner surfaces of the tank, hoses, and other attachments.
Damp wipe is the removal of mold from non-porous surfaces by wiping or scrubbing with water and a detergent. Care must be exercised to make sure the material is allowed to quickly dry to discourage any further mold growth. With surfaces such as metal, glass, hardwood, plastics, and concrete, you should scrape off as much of the mold as possible. Then, scrub the surface with a moldicide or fungicide cleaner.citation needed
High Efficiency Particulate Air filtered vacuum cleaners are used in the final cleanup of remediation areas after materials have been thoroughly dried and all contaminated materials have been removed. HEPA vacuum cleaners are recommended for the cleanup of the outside areas surrounding the remediation area. During this process the workers wear proper personal protective equipment (PPE) to prevent exposure to mold and other contaminants. The collected debris and dust should be stored in impervious bags or containers in a manner to prevent any release of debris.
Building materials and furnishings contaminated with mold should be placed into impervious bags or closed containers while in the remediation area. These materials can usually be discarded as regular construction waste.
Several types of equipment may be used in the remediation process and may include:
During the remediation process, the level of contamination dictates the level of protection for the remediation workers. The levels of contamination are described as Levels I, II, and III. Each has specific requirements for worker safety. The levels are as follows:
Small Isolated Areas (10 sq. ft or less) for example, ceiling tiles, small areas on walls.
Mid-sized Isolated Areas (10-30 sq ft) – for example, individual wallboard panels.
Large Isolated Areas (30-100 sq ft) – e.g., several wallboard panels
Extensive Contamination (greater than 100 contiguous sq. ft in an area).
In conclusion, after the moisture source has been eliminated and the mold growth removed, the premises should be revisited and the reevaluated to ensure the mold growth and the remediation process was successful. The premises should be free of any moldy smells or visible growth.
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