Mold remediation: a practical approach
Excessive mold growth in indoor environments has become an increasing health and environmental concern, as well as the subject of controversy and litigation. While human response to mold varies widely, no official medical relationship exists between exposure and human response. Nor are there any currently definitive clearance criteria or legislative guidelines for mold remediation, although a number of de facto standards and work practices are generally accepted. Still, with so much at stake, it is essential to consider several important qualifications when selecting an environmental contractor to perform mold remediation services.
Environmental mold support
Three elements are required to support mold growth: water, food, and a stable environment. Water refers not only to leaks but also to high relative humidity. If humidity is higher than 60%, carbon-based materials such as paper and wood products will absorb enough moisture to sustain and amplify mold growth.
Food sources may include unconfined cellulose (paper, dust) and wood products. A stable environment for mold translates to no sunlight, limited airflow, and minimal or no disruption.
Mold is indicative of a system or structural problem within a building that is likely to get worse if not treated. In a normal, healthy environment, the types and concentrations of fungal species found in indoor air should be identical to those present in outdoor air, indicating proper air circulation. Certain species can be indicative of HVAC or construction problems.
From a medical perspective, no official exposure/response relationship has been established. Human response to mold appears to vary widely; some people may have no reaction, while others may be extremely sensitive.
When human health is at risk, failure to act can initiate stiff OSHA penalties (General Duty Clause) for the building owner. On the other hand, many of these same physical symptoms can be related to widespread illnesses such as colds, influenza, and other allergies.
One fact that all the experts agree on is that prior to any mold remediation activities, the source of the water/moisture intrusion points must be identified and repaired. There are no current federal or state regulations for mold remediation methods or certifications of professionals involved with the remediation process. There are several peer-reviewed and accepted guidelines or standards of care that exist, which provide a good foundation to follow when faced with mold contamination in buildings.
In addition to establishing space levels for remediation, EPA guidelines have established recommendations for four cleanup methods.
Wet vacuum This is designed to collect accumulated water from floors, carpets, and hard surfaces. Do not use to vacuum porous materials such as gypsum board. It should be used only when the materials are still wet, since wet vacuums may spread spores if sufficient liquid is not present. The tanks, hoses, and attachments of these vacuums should be thoroughly cleaned and dried after use.
Damp wipe Whether dead or alive, mold is allergenic, and some molds may be toxic. Mold can generally be removed from nonporous surfaces by wiping or scrubbing with water, or water and detergent. It is important to dry these surfaces quickly and thoroughly to discourage further mold growth.
Porous materials that are wet and have mold growing on them may have to be discarded. Since molds will infiltrate porous substances and grow in empty spaces or crevices, they can be difficult or impossible to remove completely.
HEPA vacuum HEPA (High Efficiency Particulate Air) vacuums (Fig. 1) are recommended for final cleanup of remediation areas after materials have been thoroughly dried and contaminated materials removed, as well as for the cleanup of dust that may have settled on surfaces outside the remediation area.
When changing the filter, contractors should wear Personal Protective Equipment (PPE) to prevent exposure to the mold that has been captured (Fig. 2). The vacuum filter and contents must be disposed of in well-sealed plastic bags.
Discard Remove damaged materials and seal them in plastic bags before removing them from the containment area to minimize the dispersion of mold spores throughout the building. Contaminated, unsalvageable building material should be double-bagged using 6-mil poly sheeting. These bags can usually be discarded as ordinary construction waste. It is important to package mold-contaminated materials in sealed bags.
Another fact that all the experts will agree on is that 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 the work area and entering an occupied or non-abatement area. This is necessary to protect the health of building occupants and the workers performing the remediation.
Mold remediation process
According to EPA guidelines, if visible mold growth is present, sampling is unnecessary. If the source of mold contamination is unclear, or health concerns are a problem, consider sampling as part of site evaluation prior to remediation.
Sampling may help locate the source of the mold contamination, identify some of the mold species present, and differentiate between mold and soot or dirt. Post-remediation sampling may also be useful in determining whether remediation efforts have been effective.
The first step in a successful mold remediation project is to ensure the source of the microbial growth has been properly identified and corrected. A thorough visual inspection of the area is required in order to understand the order of magnitude of the visibly contaminated materials, as well as to help in the preparation of a remedial work plan.
Not always visible, mold growth can often occur behind walls and other hidden places in a building. It is critical that once the actual remediation process is begun, prudent engineering controls should be in place to mitigate/prevent hidden contamination from spreading.
Because microbial growth can occur inside HVAC systems, it is recommended that the inside of the HVAC system be visually inspected. In addition, surface sampling inside supply ducts should be performed.
If mold spores contaminate an HVAC system, and this is not identified before remediation actions occur, when that HVAC system is energized after the remediation project, it will spew mold spores back into the area that was just cleaned.
Some of the engineering controls used to secure the environment and protect building occupants and workers doing the cleanup are very similar to those utilized in the asbestos abatement industry (Fig. 3). Mold spores, like asbestos fibers, can travel on air currents and quickly spread to other areas of a building.
Post remediation testing
Because there are no scientific data to support an acceptable level of exposure to mold, there are no current EPA or OSHA regulations or standards for airborne mold contaminants. How does one know when the mold remediation/cleanup has been successful? EPA guidelines clearly indicate the following:
The water or moisture problem must be completely taken care of
Mold removal must be complete, with no visible mold, mold-damaged materials, or mold odors present
Samples of the kinds and concentrations of mold and mold spores should be similar to those found on the outside
The site should be revisited and show no signs of water damage or mold growth
People should be able to occupy or re-occupy the space without health complaints or physical symptoms.
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Examples of mold organisms and sources
Alternaria species — HVAC system problems
Stachybotrys charatrum — water and rot conditions (very prevalent)
Pencillium/Aspergillus species — (almost exactly alike) — soil and wood rot
Fusarium species — cellulose/water rot
Suggested engineering controls
HEPA-equipped air filtration devices to filter the air in the contaminated areas as well as assist in establishing a negative air pressure environment
Polyethylene sheeting affixed to walls, ceilings, and floors to seal or contain the work areas from areas that are not to be abated
Air-locks and decontamination chambers that allow for worker ingress/egress.
Mold remediation contractor qualifications
Demonstrated experience/expertise in mold/microbial remediation
Insurance covering all pollutants, with no exclusion for microbial matters
Resumes of key project personnel demonstrating commitment to industry by participating in training courses and earning industry recognized certifications i.e., NADCA, IAQA, IAQC, NREP, IICRC
Proof of written work practices and procedures specifically for microbial remediation
Demonstrated expertise in the effective operation of HEPA-filtered equipment, including a written equipment operationprogram and written integrity testing program for HEPA equipment
Documentation of participation in OSHA mandated safety programs; i.e., respiratory protection programs, etc.