Mold In Duct Study

FUNGAL COLONIZATION OF AIR-DUCTS IN THE U.S.A.

Chin S. Yang, Ph.D.
P & K Microbiology Services, Inc., 1950 Old Cuthbert Road Unit L, Cherry Hill, New Jersey, 08034 USA

Nearly one thousand and two hundred bulk samples of fiber-glass air-duct liner (FGL) collected in 2004 from the heating, ventilating, and air-conditioning (HVAC) system throughout the United States were analyzed for fungal contents.

Because FGL is porous and often traps fiber and particles, including fungal spores, the recovery of fungi from FGL is not necessarily an indication of fungal colonization.

Approximately 50% of the samples evaluated were considered to have fungal growth and colonization. Species of Cladosporium and Penicillium were the most frequently encountered colonizers. These two genera of fungi were often recovered from FGL samples taken from locations with high relative humidity, such as air ducts downstream from the coils and the blower, or buildings in humid geographical areas (such as Florida and Texas). FGL samples taken from locations where liquid water is often present, such as at cooling coils or drain pans, were dominated by high water activity fungi, such as Acremonium spp., Aureobasidium pullulans, Exophialaspp., Paecilomyes marquandii, Phoma spp., Rhodotorula spp., and yeasts.

INTRODUCTION
Fungal contamination in buildings and its impact on indoor air quality (IAQ) are well documented . A recent review from the U.S. Public Health Service, Division of Federal Occupational Health, indicated that 1/3 of indoor air quality problems may be microbe related .

Fiber-glass liners (FGL) are commonly used for acoustical and thermal insulation inside the air handler and its associated air ducts. It is a very useful material for the described purposes. However, Morey and Williams suggested that fungal growth and amplification were likely to occur in soft, porous insulation materials. Fibrous glass insulation liners, were reported to be the primary source (92%) of microbial contamination in the studies .