Mold growth, assessment, and 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.

Mold remediation is the process of removal and/or cleanup of mold from an indoor environment.

Introduction
Molds and fungi are found everywhere inside and outside. They 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. Without molds we would be inundated with dead organic matter. It has been estimated that 40 percent of United States homes have some form of mold problem.

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.

Health effects
The problems with mold usually stem from the symptoms and health effects resulting from indoor mold exposure. There is public awareness that exposure to mold can cause adverse health effects, symptoms, and possible allergic reactions. Health professionals are often tasked with the investigation and/or assessment of these health effects on employees and/or the public.

The most common form of hypersensitivity is caused by the direct exposure to inhaled mold spores or hyphal fragments which can lead to allergic asthma or allergic rhinitis. The most common effects are runny nose, watery eyes, coughing and asthma attacks. Another form of hypersensitivity is hypersensitivity pneumonitis (HP). This is usually the direct result of inhaled large spores or fragments in an occupational setting. About 5% of individuals are predicted to have some allergic airway symptoms from molds over their lifetime.

Toxic effects from mold are produced by exposure to the mycotoxins of some mold species, such as Stachybotrys chartarum (S. chartarum). These are often referred to as “Toxic molds” These toxic molds are often implicated as a potential cause of Sick Building Syndrome. A 1993-94 case study based on cases of pulmonary hemorrhage in infants in Cleveland, Ohio originally concluded there was no causal relationship between the exposure and the disease. The investigators revisited the cases and established a link to the exposure to S. chartrum and the infants in their homes. This relationship was later disproved by a different panel and re-evaluation.

Causes / Growing conditions
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 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 is the food source (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:


 * Nutrients: Food for spores in an indoor environment is organic matter, often cellulose.
 * 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, 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 humidified artificially 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.

Methods for killing mold
Methods for killing mold include exposure to high heat, dry air, sunlight (particulary UV light), ozone, and application of fungicides. Many techniques are effective in killing the mold colony but not the mold spores, as the spores tend to be more resiliant. Perhaps the simplest antifungal treaments are oxidizers (e.g. Sodium percarbonate), bases (e.g. chlorine bleach which is also an oxidizer) and acids (e.g. acetic acid and sulfuric acid), but careful usage is important as these chemical are dangerous and pose their own health hazard when used in high concentrations. Quaternary ammonium compounds (e.g. Benzalkonium chloride) found in disenfectants products such as Lysol also have fungicidal properties.

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 the need for sampling for specific species of mold is unnecessary.

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.

The key to mold control is moisture control. It is important to dry water damaged areas and items within 24-48 hours to prevent mold growth. If mold is a problem in your home, clean up the mold and get rid of the excess water or moisture. Fix leaky plumbing or other sources of water. Wash mold off hard surfaces with detergent and water, and dry completely. Absorbent materials (such as ceiling tiles & carpet) that become moldy may have to be replaced.

Mold Inspections should be performed by a party certified as a Council-certified Indoor Environmentalist or Council-certified Microbial Investigator by the American Indoor Air Quality Council. In the state of Texas there is legislation dictating who can and cannot perform investigation. There are several other organizations who claim to certify, however the IAQ Council is the CESB standard for the mold practice. [citation needed]

Sampling
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. 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 asses 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.

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.

Four steps of professional mold remediation

 * Containment: Technicians isolate the area of contamination to minimize the spread of mold spores to other areas of the home.
 * Filtration: HEPA air filters and negative air machines run continuously throughout the project. Mold spores, dust, MVOCs, gaseous compounds (i.e. Radon), and other airborne debris are removed from the air.
 * Removal and Cleanup: Contaminated materials that cannot be cleaned are removed according to mold remediation standards. Sheetrock, carpet, furniture, and other damaged materials will have to be replaced to prevent mold from returning.
 * Structural Repair, Replacement and Modification: If moisture is still present, no level of remediation effort will be successful. The source and cause of the moisture must be eliminated.  This can be a very costly step, as it involves structural repair/replacement (e.g. roof or foundation repairs), and/or structural modifications (e.g. water pumps, new ventilation systems).

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.

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.

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.  Moisture meters have a small probe that is inserted into the material, or pressed directly against the material's surface.  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.
 * PPE: includes respirators, gloves, impervious suit, and eye protection. These items can be used during the assessment and remediation processes.

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 preformed 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 from contamination and debris.

Level II
Mid-sized Isolated Areas (10-30 sq. ft) – for example, individual wallboard panels.
 * Remediation can be conducted the regular building staff as long as they are trained as for Level I. Respiratory protection, occupation of 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 from 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 decontaminated 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 soaking) 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 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.