Mold growth, assessment, and remediation
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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.
Contents
Health effects
Molds are ubiquitous in nature, and mold spores are a common component of household and workplace dust. However, when spores are present in large quantities, they are 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. The term "toxic mold" refers to molds that produce mycotoxins, such as Stachybotrys chartarum, not to all molds.[1] 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.
Causes & growing conditions
Molds are found everywhere inside and outside, and can grow on almost any substance when moisture is present. Molds reproduce by 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. Mold is normally found indoors at levels that do not affect most healthy individuals.
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 water or moisture indoors. Mold growth may also be caused by incomplete drying of flooring materials such as concrete.[2] Flooding, leaky roofs, building maintenance problems, or indoor plumbing problems can lead to mold growth inside homes, schools, or office buildings.
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 such a problem. The right conditions reactivate mold. Studies also show that mycotoxin levels are perceptibly higher in buildings that have once had a water incident (source: CMHC).
Spores need three things to grow into mold:
- Nutrients: Cellulose is a common food for spores in an indoor environment.
- Moisture: Moisture is required to begin the decaying process caused by the mold.
- Time: Mold growth begins between 24 hours and 10 days from the provision of the growing conditions. There is no known way to date 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, fabrics, and dust containing 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. People residing in a house also contribute moisture through normal breathing and perspiration. Insufficient ventilation can further enable moisture build-up. 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 °C) also has an inhibiting effect on mold growth.[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. 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 placed externally on the air ducts, because internal insulation provides a dust capture and breeding ground for mold.
Assessment
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, sampling for specific species of mold is unnecessary.[3]
These methods, considered non-intrusive, only detect visible and odor-causing molds. 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.
Sampling
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:
- Air sampling: the most common form of sampling to assess the level of mold. Sampling of the inside and outdoor air is conducted and the results to the level of mold spores inside the premises and outside are compared. Often, air sampling will provide positive identification of the existence of non-visible mold.
- Surface samples: sampling the amount of mold spores deposited on indoor surfaces (swab, tape, and dust samples)
- Bulk samples: the removal of materials from the contaminated area to identify and determine the concentration of mold in the sample.
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.[4]
Though it may not be recommended, air sampling following mold remediation is usually the best way to ascertain efficacy of remediation, when conducted by a qualified third party.[5]
Remediation
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:
- Sunlight
- Ventilation
- Non-porous building materials
- Household cleansers
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 heating, ventilating, and air conditioning, and dry fog.
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.
New technology also allows some mold remediation companies to fill a room with a dry fog that kills the mold and stops its growth. This fog uses a chemical that is EPA approved and does not harm or damage the physical well being of persons or animals.
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 negative 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.[6]
Cleanup and removal methods
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.
Dry ice freeze blasting
Recently, some companies have begun using dry ice freeze blasting to remove mold from suitable surfaces, such as wood and cement.
Dry Fog
New technology is pointing to a dry chemical fog that fills a room and kills the mold throughout a specified area. This procedure allows mold to be remediated without the destruction or damage of the facility in question. It is also safe and far less expensive then older and more traditional remediation methods[citation needed] .
Vacuum
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
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, mold should be scraped off as much as possible. Then, scrub the surface with a moldicide or fungicide cleaner.[citation needed]
HEPA vacuum
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.
Disposal of debris and damaged materials
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.
Equipment
Several types of equipment may be used in the remediation process and may include:
- Moisture meter: a tool that measures the moisture level in building materials. It can also be used to measure the progress of the drying of damaged materials. Pin moisture meters have a small probe that is inserted into the material. Pinless moisture meters usually have a flat sensing area that is pressed directly against the material's surface.[7] Moisture meters can be used on carpet, wallboard, woods, brick, and other masonry.
- Humidity gauge: measures the amount of humidity in the indoor environment. Often gauges are paired with a thermometer to measure the temperature.
- Borescope: a hand-held tool that allows the user to see potential mold problems inside walls, ceilings, crawl spaces, and other tight spaces. It consists of a camera on the end of a flexible “snake”. No major drilling or cutting of dry wall is required.
- Digital camera: used to document findings during assessment.
- Personal protective equipment (PPE): includes respirators, gloves, impervious suit, and eye protection. These items can be used during the assessment and remediation processes.
- Thermographic camera : Infrared thermal imaging cameras are often used (and effective) in addition to moisture meters to double check moisture meter findings, and look at the broader picture. They help mainly in identifying auxiliary points of moisture intrusion.
- Dehumidifier :[citation needed] If you have high humidity in your home from things like aquariums or house plants, a dehumidifier can help bring down the level of moisture in the air. This in turn will reduce the chances that mold can build up within these areas of your home.
Protection levels
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:
Level I
Small Isolated Areas (10 sq. ft or less) for example, ceiling tiles, small areas on walls.
- Remediation can be conducted by the regular building staff as long as they are trained on proper clean-up methods, personal protection, and potential hazards. This training can be performed as part of a program to comply with the requirements of OSHA Hazard Communication Standard ( 29 CFR 1910.1200).
- Respiratory protection (for example, N-95 disposable respirator) is recommended. Respirators must be used in accordance with the OSHA respiratory protection standard (29 CFR 1910.134). Gloves and eye protection should also be worn.
- The work area should be unoccupied. Removing people from spaces adjacent to the work area is not necessary, but is recommended for infants (less than 12 months old), persons recovering from recent surgery, immune-suppressed, or people with respiratory diseases.
- Containment of the work area is not necessary. However, misting and dust suppression is recommended.
- Contaminated materials that cannot be cleaned should be removed from the building in sealed impermeable plastic bags and disposed of as ordinary waste.
- The work area/areas used by workers for access/egress should be cleaned with a damp cloth or mop and a detergent.
- All areas should be left dry and visibly free of contamination and debris.
Level II
Mid-sized Isolated Areas (10-30 sq ft) – for example, individual wallboard panels.
- Remediation can be conducted by the regular building staff as long as they are trained as for Level I. Respiratory protection, occupation of the work and adjacent areas, and handling of contaminated materials are the same as for Level I.
- Surfaces in the work area that could become contaminated should be covered with sheet(s) of plastic that are secured in place. This should be done prior to any remediation process to prevent further contamination.
- Dust suppression methods, such as misting (not soaking) surface prior to remediation, are recommended.
- The work area/areas used by workers for access/egress should be HEPA vacuumed and cleaned with a damp cloth or mop and a detergent.
- As with Level I, all areas should be left dry and visibly free of contamination and debris.
Level III
Large Isolated Areas (30-100 sq ft) – e.g., several wallboard panels
- Industrial hygienists or other environmental health and safety professionals with experience performing microbial investigations and/or mold remediation should be consulted prior to remediation activities to provide oversight for the project.
- It is recommended that personnel be trained in the handling of hazardous materials and equipped with respiratory protection (N-95 disposable respirator). Respirators must be used in accordance with OSHA respiratory protection standard (29 CFR 1910.134) Gloves and eye protection should also be worn.
- Surfaces in the work area and areas directly adjacent that could become contaminated should be covered with a secured plastics sheet(s) before remediation to contain dust/debris and prevent further contamination.
- Seal ventilation ducts/grills in the work area and areas directly adjacent with plastic sheeting.
- The work area and areas directly adjacent should be unoccupied. Removing people from spaces adjacent to the work area is not necessary, but is recommended for infants (less than 12 month old), persons recovering from recent surgery, immune-suppressed or people with respiratory diseases.
- Dust suppression methods, such as misting (not soakings) surface prior to remediation, are recommended.
- Contaminated materials that cannot be cleaned should be removed from the building in sealed impermeable plastic bags and disposed of as ordinary waste.
- The work area/areas used by workers for access/egress should be HEPA vacuumed and cleaned with a damp cloth or mop and a detergent.
- All areas should be left dry and visibly free from contamination and debris.
Level IV
Extensive Contamination (greater than 100 contiguous sq. ft in an area).
- Personnel trained in handling of hazardous materials and equipped with:
- Full face respirators with HEPA cartridges
- Disposable protective clothing covering the entire body including the head, shoes and hands
- Containment of the affected area:
- Complete isolation of the work area from occupied spaces using plastic sheeting sealed with duct tape ( including ventilation duct/grills, fixtures, and other openings
- The use of an exhaust fan with a HEPA filter to generate negative pressurization, a decontamination room, and airlocks
- Contaminated materials that cannot be cleaned should be removed from the building in sealed impermeable plastic bags and disposed of as ordinary waste.
- The contained area and decontamination room should be HEPA vacuumed and cleaned with a damp cloth or mopped with a detergent solution and be visibly clean prior to the removal of any isolation barrier.
In conclusion, after the moisture source has been eliminated and the mold growth removed, the premises should be revisited and then re-evaluated to ensure the mold growth and the remediation process was successful. The premises should be free of any moldy smells or visible growth.
See also
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- Environmental engineering
- Environmental health
- GREENGUARD Environmental Institute
- High Ozone Shock Treatment for mold remediation
- Indoor air quality
- Occupational asthma
- Occupational safety and health
- Sick building syndrome
Notes
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<references />, or <references group="..." />External links
- Environmental Protection Agency - Mold Homepage
- Minnesota Department of Health - Limitations of Mold Testing
- CCA 82 - Mould Guidelines for the Canadian Construction Industry
- American Indoor Air Quality Council
- Institute of Inspection, Cleaning and Restoration Certification
- Fighting Mold—The Homeowners' Guide(Canada Mortgage and Housing Corporation)
- Mold Moisture and Your Home An article by the International Association of Certified Home Inspectors (InterNACHI)
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- Occupational safety and health
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