IAQ Problem Solving

With growing awareness of indoor air quality (IAQ) issues, especially microbial contamination, environmental professionals must be ready to react appropriately to protect businesses and their property and employees, as well as to prevent detrimental publicity. Such IAQ issues can arise through building changes, collateral damage secondary to some other loss (such as fire or flooding) or possibly as a result of neglect.

No matter the cause, it is imperative that IAQ issues be addressed as expediently and effectively as possible. This article addresses some of the primary IAQ problems that may arise and suggests measures for proactively addressing them.


Heating, ventilating and air conditioning (HVAC) airflow/contaminants issues top the list when it comes to commonly found IAQ problems. Many problems arise after a time when the HVAC is shut down -- usually for economic savings. This action can backfire dramatically, resulting in the prolific growth of fungus. One major rule to follow: There is no place for energy savings in vital document storage areas and special collections. These areas require 24/7 environmental controls, and independent control of temperature and relative humidity is desirable.

Tampering with HVAC systems can also lead to problems. For example, during a hot summer month in Texas, unhappy tenants may complain about the temperature in their areas. Rather than addressing the system's cooling capacity, facilities personnel close off the fresh air returns to get maximum cooling. This action exacerbates an existing moisture problem and concentrates various fumes in the building. After medical intervention was required in the case of several tenants, mold was found reproducing in interstitial cavities and behind cabinetry. The correction was a very expensive remediation project, proving that the core problems relating to indoor air quality must be corrected. Simply treating the symptoms in an HVAC system may lead to a more expensive outcome.

Researches still face the problem of determining what molds and how much are dangerous or deleterious to humans.

Another problem arises when the function of an existing space is converted to another use. One case occurred when an area that had been an automotive garage was converted to a school gymnasium. After multiple complaints about skin and eye irritation from the students, a certified industrial hygienist was retained. However, after exhaustive testing and examination under the gym flooring and declarations that the area was free of any IAQ problems, the complaints continued.

After examination and discussions with BMS Catastrophe's Special Technologies department, the problem was defined. In the automotive garage, mercury vapor lighting had been provided for economy. With the former garage now completely enclosed and inadequately ventilated, the heavy ultraviolet spectral output of these lamps was now generating ozone gas, the source of the irritation. All symptoms disappeared after the lighting was removed and converted. This demonstrates that expensive, exhaustive testing may not be required if you listen carefully to the complaints and keep an open mind about possible causes.

Mold and Fungus

Over the past several years, the medical community has begun the difficult task of determining the scientifically supportable health effects of mold on building occupants. Molds produce contaminants that are potentially harmful, such as mold spores, mycotoxins, glucans and microbial volatile organic compounds (MVOC). All molds, depending on the sensitivity of the receptors (i.e., occupants) and the concentration of the particular contaminant (e.g., spore, glucan, mycotoxin and MVOC), have the potential to produce adverse health effects and responses in humans. Avoiding such health effects is a critical reason for the prevention of indoor mold growth.

The scientific community has a long way to go before any comprehensive and conclusive studies are completed, however. Researchers still face the problem of determining what molds and how much are dangerous or deleterious to humans. It is still uncertain exactly how many spores per cubic meter or parts per million of glucans or MVOCs are harmful or create an indoor air quality problem. Differences in human sensitivities create an even more difficult task in quantifying contamination. Not everyone is allergic, asthmatic or sensitized to the same airborne levels of the various species of molds.

Currently, researchers and health scientists incorporate a common sense approach to quantification. In most cases, industrial hygienists and IAQ specialists measure background levels outdoors and compare results to the indoor air to determine if the environment is typical for normal human occupancy. Although not an exact science, this technique has been useful for specialists in determining the presence of hidden molds or undetected amplification sites and in post-remediation clearance testing.

In most cases, industrial hygienists and IAQ specialists measure background levels outdoors and compare results to the indoor air to determine if the environment is typical for normal human occupancy.

The equation for mold growth is simple: mold spores plus sufficient moisture plus sufficient nutrients equals active growth. Temperature is an additional factor in the equation. As noted, mold spores are almost always present in the air, in outdoors and indoors. Building materials are manufactured with products that are rich with nutrients fed upon by fungi. Indoor temperatures remain at a comfortable level for human occupancy. The only factor that is typically not present is moisture. Therefore, the best factor to manipulate for eliminating or controlling mold growth is moisture.

Problems occur when mold spores come in contact with building materials (e.g., sheetrock, wallpaper, carpet, ceiling tile, etc.) that have sufficient moisture content to support active fungal growth. If the moisture content of the materials and their substrates is in the proper range for a sufficient period of time, a mold problem can develop rapidly. Once growth begins, it amplifies quickly, releasing millions of spores into the air and degrading organic building materials and other carbon-based sources. As the propagation of spores occurs in the airspace, the potential for building related syndrome (BRS) (also known as sick building syndrome) and occupant complaints is significantly increased.

Buildings can develop mold growth from a single water intrusion, such as a leaking roof, window or pipe. The water intrusion could be an acute catastrophic event or just a slow chronic problem that goes undetected for a considerable length of time. Mold can grow undetected inside a wall cavity, behind vinyl wallpaper or anywhere the moisture level and nutrient availability are sufficient.

Therefore, it is critical that a building is dried immediately and sufficiently after a water intrusion. The U.S. Environmental Protection Agency (EPA) recommends water mitigation within 24 to 48 hours of water intrusion. A qualified contractor should be contacted immediately after water loss is discovered. The contractor should be experienced and have the resources to properly remove the water, dry the affected areas, and dehumidify the entire building. Building managers should be proactive and educate their maintenance personnel in the detection and mitigation of water losses.

Construction defects are also a frequent cause of mold claims. These defects can result from inferior building components and materials or from improper installation and construction practices. In the case of exterior siding, or other enclosed components, the contamination and associated damage can be substantial since the mold is so widespread by the time it is detected. Construction defects cases can cost millions of dollars and time to remove the moisture, remediate the mold and rebuild both the structural and cosmetic damage.

Another very common reason that mold develops in a building is poor stewardship. The HVAC system can be the cause or the cure when it comes to indoor mold growth. Improperly maintained, the HVAC can become the mold amplification site due to condensation and buildup of debris. Excessive moisture-generating activities can contribute to the problem and raise indoor relative humidity above 70 percent, which is ideal for mold growth. Even when exterior water sources are minimized, moisture in the indoor air can build up from poorly vented combustion appliances, showers, cooking, laundry, human respiration, etc.

Strategies for Controlling Mold/Fungus

The following are various strategies that can aid in the control of building humidity and moisture:

  • Dilute humid indoor air with dry air via the air handling system.
  • Control the source of the water by repairing water leaks. Properly ventilate the air space that is humidified by activities that increase indoor moisture levels.
  • Control sources of water or leaks outside of the building envelope by improving drainage, thus moving water away from the building, and waterproofing windows and other potential entry points.
  • Increase ventilation - stagnant air tends to increase in relative humidity quicker than moving air, increasing the potential for migration of indoor humidity into hidden wall cavities.
  • Employ dehumidification to remove moisture from the air space and building materials. Refrigerant or desiccant dehumidification can be used depending on the circumstances.

Seeking Outside Help With IAQ Issues

The following factors should be monitored in determining when and whether to seek outside expert help:

  • Complaints and concerns from tenants and/or employees.
  • The intervention of a health professional when building IAQ may be causative of health issues.
  • Extensive new construction.
  • Significant change in the function of an existing area.
  • Building trauma/disaster, such as a flood, tornado, fire, etc.
  • Excessive moisture in the HVAC.

Once a problem has been detected, contact an outside specialist immediately. The factors relating to poor indoor air quality are numerous and usually require a professional indoor air quality specialist or building scientist to conduct an investigation and assessment in order to determine the cause and origin of the problem. It helps to check the experience level and specialties of each firm. They should be able to provide references for similar investigations in your industry and within the physical limitations similar to your facility.

The best factor to manipulate for eliminating or controlling mold growth is moisture.

The investigation and assessment of IAQ concerns should be defined by a detailed scope of work document, which should include a list of deliverables, project time and milestones and a careful breakdown of costs associated with the investigation and assessment. A nondisclosure/ confidentiality agreement is also a good safety measure.

When the indoor air quality is determined by the specialist to be poor as a result of indoor mold, an experienced and qualified IAQ specialist should then prepare a comprehensive plan of action. The plan should outline the problem areas, identify the offensive contaminant and specify appropriate levels of containment. Specifically state how the problem is to be corrected or remediated, and suggest a clearance level that should be attained through remediation and verified by appropriate testing methods. All workers should utilize personal protective equipment during the remediation activities.

In most cases, a qualified and experienced remediation contractor will then be retained to remove the contamination. Once the remediation activities are completed, the consultant will conduct post-remediation testing in order to verify that the remediation process was successful. Retaining the right outside contractor expeditiously will ensure that the final product is satisfactory, successfully completed and not open to costly litigation or publicity.


Public database search for persons certified for the practice of industrial hygiene by the American Board of Industrial Hygiene -- www2.abih.org/query/ABIH_roster.asp

U.S. Environmental Protection Agency (EPA) Web site on mold remediation in schools and commercial buildings -- www.epa.gov/iaq/molds/intro.html

EPA Web site on indoor air quality publications and resources -- www.epa.gov/iaq/pubs/moldresources.html

Center for Disease Control National Center for Environmental Health Web site on molds -- www.cdc.gov

American Bar Association's Web site featuring the legal article, "Mold: An Emerging Construction Defect," by Alexander Robertson IV, JD -- www.abanet.org/genpractice/magazine/aprilmay2001/robertson.html

This article originally appeared in the May 2002 issue of Environmental Protection, Vol. 13, No. 5, p. 24.

This article originally appeared in the 05/01/2002 issue of Environmental Protection.

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