The Mold Matrix: Innovations in Risk Assessment and Remediation

Dec. 1, 2004
Based on system thinking, these guidelines can help you determine the severity of your mold problem, and the ideal methods and precautions for remediation.

Mold is an insidious material that at its very early stages is quite natural and unassuming. It is a naturally occurring biological contaminant with some positive characteristics, including the ability to break down leaves, wood and other plant debris.

In the indoor environment, however, unidentified and unremediated mold can be as significant and costly as most any environmental hazard. Water incursion and damp buildings are the primary sources of mold. Mold can survive almost anywhere with water and humidity (usually where relative humidity exceeds 60 percent). Standing water, water-damaged materials and wet surfaces also serve as a breeding ground for mold. There is no practical way to eliminate all mold and mold spores in the indoor environment; the best way to control mold growth is to control moisture.

Despite its stealthy nature, mold can be tested for, controlled, remediated and prevented through the use of tried-and-true methods and leading-edge technologies. In all cases, mold testing, control and remediation should be left to experts who understand the potential hazards and best practices.

Everyone, it seems, has a stake in ensuring that potential environmental hazards such as mold are addressed in a proactive, systematic way, but who knows for sure what's right? There are currently no nationwide standards or guidelines in place for environmental testing, remediation techniques, contractor qualifications, and worker training and protective equipment. Many specifications reference the pioneering New York City guidelines, which are clearly outdated for today's world. For example, the guidelines state that no containment is required for 10 square feet or less of active mold growth. However, recent research has measured up to 1 billion mold spores per square foot of drywall the uncontained removal of which could lead to a severely contaminated facility!

So what can we do about the lack of consensus? Experienced professionals have an opportunity to be innovative and an obligation to pursue "best of the best" innovations to guide their activities. In LVI Services' experience, a three-step systems approach to mold risk assessment and remediation is essential. Such analysis enables building owners/managers and contractors to make risk-based determinations of which remediation measures and precautions are necessary.

Step One: Identify Type of Remediation Project

Mold remediation projects can be broken down into four basic types, based on the severity of the problem and the amount of corrective action required. In many ways, the mold remediation systems approach is similar to infection control best practices used in hospitals.

Type A (inspection and non-invasive activities) includes, but is not limited to:

  • Removal of ceiling tiles and minimal destructive techniques for visual inspection
  • Bulk, tape and/or surface sampling
  • Establishment of containment barriers

Type B (small-scale, short-duration activities which create minimal dust) involves:

  • Stains on non-porous surfaces that can be wiped clean
  • Small spot of growth on ceiling tile or pipe insulation
  • Small spill on carpet

Type C covers remediation work that generates a moderate to high level of dust or requires demolition or removal of any fixed building components. Examples here include:

  • Minor sheetrock removal and/or wall covering
  • Significant removal of ceiling tile and insulation above tiles
  • Minor duct cleaning and other work above ceilings
  • Removal of non-cleanable carpet
  • Any individual remediation activity that cannot be completed within a single work shift or weekend

Type D (major remediation projects) typically includes:

  • Activities that require consecutive work shifts, and the potential for unauthorized personnel exposure
  • Significant heavy mold growth throughout a building
  • "Toxic" species of mold present
  • Major contamination of ductwork and air handling system

Step Two: Identify Potential Exposed Individuals

Once you identify what kind of project you have, you are ready to consider "the people factor," the building occupants who are potentially exposed to the mold and may need to be protected during remediation. We have identified four categories of people:

  • Low risk, which includes transient employees (which could include short-term workers and workers who are in and out of the building frequently) and healthy adults.
  • Medium risk, which includes teenagers, healthy elderly individuals and individuals exposed to the mold greater than 8 hours per day.
  • High risk, which includes pregnant women, individuals on prescription medication or recovering from surgical procedures, and children between 6 months and 12 years old.
  • Highest risk, which includes immuno-suppressed individuals, people receiving oncology treatment, sufferers of emphysema or other respiratory diseases, and infants.

Step Three: Create the Remediation/Precautions Matrix

The results of steps one and two can be plotted in a matrix to help determine what level of remediation activities and precautions need to be taken to achieve a positive outcome. Again, we have identified four classes of remediation projects. (See matrix at left.)

Classes I and II are relatively easy to initiate, and can be completed rather quickly with minimal impact on building inhabitants. Class I, for example, requires basic good housekeeping procedures such as minimizing dust, using drop cloths and cleaning up with HEPA-filtered vacuums. Class II is somewhat more intensive, with requirements for using EPA-registered disinfectants, containing construction waste, and limiting access to potentially contaminated work areas via minimal containments.

Classes III and IV require significant long-term control measures. For Class III remediation projects, we recommend the following:

  • Remove or isolate the HVAC system in areas where work is being done to prevent contamination of duct system.
  • Erect hard critical barriers, i.e. sheetrock, plywood or plastic, to seal mold work area from the rest of the building.
  • Utilize HEPA-equipped air filtration units to maintain negative air pressure within the work area.
  • Require everyone entering the work area to wear personal protective equipment, including full-body coverings (disposable), gloves and half-mask HEPA filter respirators.
  • Conduct daily supervisor walkthroughs at the beginning and end of every shift to verify integrity of critical barriers and negative pressure.
  • Contain remediated waste before transport in tightly covered containers.
  • Clean and decontaminate all equipment and protective equipment prior to final wipe down of the area.

Class IV projects require all of the above, plus measures such as:

  • Cover all structures and equipment not being cleaned or removed.
  • Wear rubber boots and full-face respirators (for remediation workers), in addition to the full-body coverings and gloves mentioned above.
  • Construct a decontamination facility and require all personnel to pass through it before leaving work site
  • Conduct exterior air monitoring throughout the duration of the project
  • Consider evacuating high-risk individuals, at least during the most hazardous portions of the project, i.e. during large-scale demolition.

Other Best Practices

Best practices and leading-edge innovations for mold control and remediation continue to evolve. Traditional remediation measures include surface cleanup with detergent and water, HEPA vacuuming, and replacement of mold-laden building materials.

In addition, in LVI's experience, two other best practices that may appear to be obvious continue to cause problems for building owners and remediation firms.

First, many organizations fail to identify all of the sources of unexpected intrusion of water into a facility. They stop looking for mold sources as soon as they find one and then they correct the problem, only to find out that other sources of moisture are also feeding the problem.

Second, organizations must realize that health considerations (notably allergic reactions, asthma and other respiratory complaints) are not the only reason to pursue mold control and remediation. Mold is a parasitic saprophyte, which means it cannot manufacture its own food; instead it derives its nutrients from the materials on which it is growing. As a result, mold is capable of causing significant structural damage to buildings.

Innovations in Remediation

For severe or unusual cases, there are a number of innovative tools and methods that are just beginning to gain widespread acceptance. Here is a summary of some of the more interesting innovations:

n Disinfectant biocides introduce a potentially hazardous substance into the indoor environment to deal with another hazardous substance. The American Industrial Hygiene Association has specifically decided not to recommend biocides. But at LVI, we have been using biocides for almost 10 years, in conjunction with detailed cleaning and careful component removal. We have never had a complaint about biocide-related health effects in more than 500 mold remediation projects, and we have never been called back due to mold re-growth where biocides were used. Such results demonstrate that biocides have a role in the mold remediation field and may ultimate become the best of the best practices.

Remember, many states require a contractor to have a pesticide application license in order to apply biocides, which should only be applied in accordance with manufacturers' labeling requirements.

n Fungal-inhibiting sealants (or encapsulants) have become controversial because some disreputable contractors have been using sealants to cover up existing mold. In our experience, that is unacceptable. Fungal-inhibiting compounds should only be used to protect cleaned-up surfaces from a recurrence of mold. Some progressive builders and designers are putting fungal-inhibiting sealants in the wall cavities of new buildings as they are being constructed. It may be the best "mold insurance" you can get.

Researchers and environmental firms are also working on a number of additional emerging technologies, including the use of gamma radiation, high heat and chlorine dioxide "dry gas" for mold remediation. We in the environmental industry need to continue to challenge the status quo and drive our best practices to the highest possible level. The art and science of mold remediation have come a long way in recent years, but clearly there are even more opportunities for success and innovation.

Alfred C. Draper III is an industrial hygienist, chemist and toxicologist who has been with New York City-based LVI Services Inc. and its subsidiaries for 17 years. He currently serves as director of LVI Restoration, which focuses on issues such as mold, infection control, hazardous materials and emergency response. With more than 25 offices across the United States, LVI Services is the nation's largest environmental services firm in its specialty, which includes large demolition and remediation projects involving asbestos, lead paint, mold, infection control, hazardous materials and emergency response. For more information, visit

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