Understanding Fungal Contamination in Indoor Environments

During warmer weather the emphasis on assessing and controlling indoor air quality tends to focus on microbiological issues, especially fungus contamination.  Along with maintaining a balance between energy efficiency, acceptable indoor environments, and cost effectiveness, building professionals must now consider an increasing number of tenant complaints resulting from reactions to fungal contamination, increase their understanding of fungi, and develop methods to deal with fungal contamination in their facilities.

More than 100,000 species of fungus have been identified, including mildews, molds, mushrooms, and yeasts and although they more closely resemble animals, are classified as a separate kingdom.  Some species of fungus are harmless or beneficial, and are, for example, essential to the production of bread, alcoholic beverages, and many antibiotics.  Fungus diseases, however, result from damage to body tissue as harmful fungi use parts of our cells for nutrients or release potent toxins.  Common fungal illnesses range from allergic reactions of varying severity to superficial infections, broncho-pulmonary infections, sinus infections, asthma, hay fever, and alveolitis and are largely based on the individual's sensitivity to each fungus present.

Elevated moisture is the major contributor to indoor micro-biological activity and when materials are obviously damp or wet, or humidity is greater than 75%, there is greater opportunity for fungal growth.  The severity of growth is further influenced by the amount of time materials are allowed to remain wet and undisturbed.  Since humidity is usually greater at material interfaces than in ambient air, most documentation warns of indoor humidity above 60%, and advises, for optimum drying after water intrusion, humidity be reduced and maintained below 50% and preferably below 40% as quickly as possible.

Along with moisture, the type and quantity of nutrients and air velocity play an important role in the growth of microorganisms.  Basically, a dirty environment provides more nutrients for mold growth than a clean environment and dust, dirt, and materials such as wood, paper, adhesives, acoustical fiber, drywall, plaster, paints, and textiles provide an environment ideal to spore germination and growth.  Most indoor fungi grow best when the ambient air is stagnant and do not grow well when air velocity is greater than two feet per second.

Spore counts considerably higher in indoor air as compared to outdoor air may indicate accelerated fungal growth and the possibility of contamination.  It is important to address the root causes of mold growth aggressively and to establish a plan to maintain an environment that provides human comfort while inhibiting mold growth.  Repair of the defects that led to water accumulation or elevated humidity should be conducted in conjunction with or prior to fungal remediation.  The U.S. EPA has published a guideline titled Mold Remediation in Schools and Commercial Buildings (EPA 402-k-01-001, March, 2001) recommending an immediate response (within 24 to 48 hours) and thorough clean up, drying, and/or removal of water damaged materials to prevent or limit mold growth.  Non-porous and semi-porous materials that are structurally sound and visibly moldy can be cleaned and reused.  Porous materials and wallboards with more than a small area of contamination should be removed and discarded.  Specific methods of assessing and remediating fungal contamination should be based on the extent of visible contamination and underlying damage.

By increasing their understanding of fungi and methods for dealing with fungal contamination in their facilities, building and construction professionals can develop a pro-active plan to minimize moisture sources and keep building spaces clean and free of debris, and develop protocols to deal effectively with materials that inadvertently become wet or damp.  Indoor air quality consultants can offer advice and services relating to fungi/mold issues including investigative and assessment services, remediation programs, and air quality monitoring.  In the absence of pro-active planning, a quick, knowledgeable, and tactful assault on any complaint deriving from actual or suspected fungal contamination will make the difference between a successful mitigation of the problem and an antagonizing, problematic, conflict ridden project.

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