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.

Health effects[edit]

Main article: Mold health issues

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.

Symptoms of mold exposure[edit]

Symptoms of mold exposure can include:[2]

Health effects linking to asthma[edit]

Infants may develop respiratory symptoms as a result of exposure to a specific type of fungal mold, called Penicillium. Signs that an infant may have mold-related respiratory problems include (but are not limited to) a persistent cough and/or wheeze. Increased exposure increases the probability of developing respiratory symptoms during their first year of life. Studies have shown that a correlation exists between the probability of developing asthma and increased exposure Penicillium. The levels are deemed no mold to low level, from low to intermediate, from intermediate to high.[3]

Mold exposures have a variety of health effects depending on the person, some people are more sensitive to mold than others. Exposure to mold can cause a number of health issues such as; throat irritation, nasal stuffiness, eye irritation, cough and wheezing, as well as skin irritation in some cases. Exposure to mold may also cause heightened sensitivity depending on the time and nature of exposure. People at higher risk for mold allergies are people with chronic lung illnesses, which will result in more severe reactions when exposed to mold.

There has been sufficient evidence that damp indoor environments are correlated with upper respiratory tract symptoms such as; coughing, and wheezing in people with asthma.[4]

Causes & growing conditions[edit]

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. Flooding, leaky roofs, building maintenance problems, or indoor plumbing problems can lead to mold growth inside. Interior moisture vapor commonly condenses on surfaces cooler than the moisture containing air which enables mold to flourish.[5] This moisture vapor passes through walls, ceilings and condenses typically in the winter months in climates where the heating cycle is extended. Floors over crawlspaces and basements (without vapor barriers or with dirt floors) are also problem areas. (The "doormat test" is very good at detecting moisture vapor emanating from under concrete slabs that are missing a sub-slab vapor barrier.[6] )

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).

Although this home suffered only minor exterior damage from Hurricane Katrina, small leaks and inadequate air flow permitted this mold infestation.

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, 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. Molds grow best in warm temperatures, 77 to 86 °F (25 to 30 °C), though some growth may occur anywhere between 32 and 95 °F (0 and 35 °C).[7]

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.)
  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 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[edit]

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.[8]

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.

Sampling[edit]

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 following 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 sampling include but are not limited to::

When sampling is conducted, all three types are recommended by the AIHA, as each sample method alone has specific limitations. For example, air samples will not provide proof of a hidden source of mold. Nor would a tape sample provide the level of contamination in the air.[9]

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.[10]

Remediation[edit]

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:

There are many ways to prevent mold growth; see heating, ventilating, improved insulation and air conditioning. 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 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.

Significant mold growth may require professional mold remediation to remove the affected building materials and eradicate the source of excess moisture. In extreme cases of mold growth in buildings, it may be more cost-effective to condemn the building rather than clean the mold to safe levels.

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.[11]

Cleanup and removal methods[edit]

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.

Evaluating mold exposures[edit]

Before beginning mold remediation you should make sure you assess the area infected with mold to ensure safety, you clean up the entire moldy area, and properly approach the mold.[8]

Cleaning recommendations[edit]

These steps should always be done by a trained professional.[12]

What to wear when removing mold[edit]

When cleaning up mold it is important to avoid breathing in mold or mold spores, as this can have major health implications. To avoid airborne mold exposure you should wear a respirator to protect your lungs. Half-face or full-face respirators have removable cartridges that will stop the mold spores from entering your nose or mouth. A full-face respirator will also protect your eyes. Be sure to follow the directions carefully, if it does not fit properly or is not put on correctly it may be ineffective.

Filters used with the respirator should ideally be rated P-100. Some cartridges also come with an activated carbon element. The carbon helps to remove the odor given off by mold and mildew.

Protective clothing should also be worn. Disposable hazmat coveralls are available to keep out particles down to one micrometer. Protective suits keep mold spores from entering any cuts on the skin.

Next be sure to wear gloves to ensure protection from mold. You should wear gloves made of rubber, nitrile, polyurethane, or neoprene so that no mold or disinfectant materials get through to your skin.

If a half-face respirator mask is used, goggles should be worn to keep mold spores from entering the mucus membrane and propagating. Appropriate goggles should not have ventilation holes so that no mold particles will get in. Full face respirators have an advantage here as the air breathed in is directed to the inside of the lens first which keeps it from fogging as you work.[8][11]

Dry brushing or agitation device[edit]

These systems are known for the removal of the biological material in the ductwork that the mold spores feed upon. A good brushing or agitation machine will break the static bond and remove the hard and soft debris in the ductwork. Dry brushing introduces nothing foreign into the HVAC system and is the only system that sweeps all surfaces.

Dry ice blasting[edit]

Recently, some companies have begun using dry ice blasting to remove mold from suitable surfaces, such as wood and cement. Soda Blasting is also a good method to remove the mold. Media Blasting, which removes mold is a preferred method to encapsulation, which only cover the mold.

Vacuum[edit]

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[edit]

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[edit]

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[edit]

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[edit]

Several types of equipment may be used in the remediation process and may include:

Protection levels[edit]

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, III, and IV. Each has specific requirements for worker safety. The levels are as follows:[13][14]

Level I[edit]

Small Isolated Areas ( 10 sq ft (0.93 m2) or less) for example, ceiling tiles, small areas on walls.

Level II[edit]

Mid-sized Isolated Areas (10-30 sq ft) – for example, individual wallboard panels.

Level III[edit]

Large Isolated Areas (30-100 sq ft) – e.g., several wallboard panels

Level IV[edit]

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 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.

Mold prevention and control[edit]

In order to avoid mold from growing in your home one should do the following:

Hidden mold[edit]

After a major storm or flood one should look out for any signs of hidden mold growth. One can detect mold by the smell and any sign of water damage on the walls or ceiling. Mold can grow in many places that are not visible to the human eye in the indoor environment. Mold is often found behind wallpaper or paneling, the topside of ceiling tiles, back side of dry wall, or the underside of carpets or carpet padding. Piping inside the walls may also be a source of mold growth since pipes often leak and cause moisture and condensation. One must also check in roof materials above ceiling tiles since roofs often leak and water collects inside the walls and insulation. If one is suspicious about mold growth one should investigate with caution to prevent exposure to mold.[8]

See also[edit]

Notes[edit]

  1. ^ Indoor Environmental Quality Dampness and Mold in Buildings. National Institute for Occupational Safety and Health. August 1, 2008.
  2. ^ Minnesota Department of Health. "Mold and Moisture in Homes". Minnesota North Star. Retrieved 22 November 2011. 
  3. ^ Gent, Janneane. "Levels of Household Mold Associated with Respiratory Symptoms in the First Year of Life in a Cohort at Risk for Asthma". Department of Epidemiology and Public Health, Yale University. Retrieved 18 November 2011. 
  4. ^ Cohen, Aaron. "WHO Guidelines for Indoor Air Quality: Dampness and Mould". World Health Organization. Retrieved 18 November 2011. 
  5. ^ "Warm Air is a Moisture Conduit". by Robert Wewer. FSI Restorations. Retrieved 1 January 2014. 
  6. ^ "The Dormat Test". by Robert Wewer. FSI Restorations. Retrieved 1 January 2014. 
  7. ^ http://www.engext.ksu.edu/moisture/mf2141.pdf
  8. ^ a b c d e "A Brief Guide to Mold, Moisture, and Your Home. EPA 402-K-02-003". U. S. Environmental Protection Agency. September 2010. Retrieved 10 May 2013. 
  9. ^ Niemeier, R. Todd, Sivasubramani, Satheesh K., Reponen, Tiina and Grinshpun, Sergey A., (2006) "Assessment of Fungal Contamination in Moldy Homes: Comparison of Different Methods", Journal of Occupational and Environmental Hygiene, 3:5, 262-273 [1]
  10. ^ IICRC(ANSI) S520 Standard
  11. ^ a b "Guidelines on Assessment and Remediation of Fungi in Indoor Environments". New York City Department of Health and Mental Hygiene. November 2008. Retrieved 10 May 2013. 
  12. ^ NIOSH. "Recommendations for the cleaning and remediation of flood-contaminated hvac system: A guide for building ovwners and managers". Center For Disease Control. Retrieved 18 November 2011. 
  13. ^ "Mold Removal Protection Levels". Environmental Protective Solutions. Retrieved 29 June 2014. 
  14. ^ "Chapter 6 - Containment and Personal Protective Equipment (PPE)". EPA. Retrieved 29 June 2014. 

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