Issue link: https://hi.iaq.net/i/675987
2 Comparison of the indoor and outdoor bioaerosol concentrations, therefore, can potentially be a good indicator of whether or not microbial amplification is occurring in a building. The significant presence of fungi in the indoor environment, which are either not present in, or are just a minor component of, the outdoor air, should be considered unacceptable from both a health perspective and a building performance point of view. (17) Over a five-year period of time, both indoor and outdoor culturable bioaerosol concentrations were studied in the Metropolitan New York region. The overall purpose of the study was to explore the relationship between the types and concentrations of airborne fungi that are found in the indoor and outdoor air. These data can be used by other indoor air quality professionals to provide some reference for typical bioaerosol concentrations found in mechanically ventilated office buildings, where samples collected in future studies can then be compared against these results in order to help determine if potential microbial problems may exist. MATERIALS AND METHODS Air Sampling Over a five-year period, a total of one hundred thirty five (135) microbial surveys were conducted in seventy six (76) different commercial office buildings in the metropolitan New York region, which includes New York City, Northern New Jersey, Western Long Island and lower Westchester County. Samples were collected on a spot basis during normal business hours, typically between 9:00 am and 5:00 pm, Monday through Friday, at a height of approximately 4 feet (the breathing zone of a seated individual). A total of seven hundred sixty four (764) culturable airborne fungal samples were collected; five hundred thirty three (533) were collected from within the buildings, and the remaining two hundred thirty one (231) were collected outdoors. All of the buildings surveyed, a majority of which are considered Class A commercial properties, were equipped with forced heating, ventilating and air conditioning (HVAC) systems. In general, the HVAC systems were equipped with pre-filters followed by either medium- to high-efficiency bag or box-type secondary filters. Data from surveys where an obvious microbial problem had been identified (e.g., flooding with subsequent visible growth) were not included in this study. Sampling for culturable species of airborne fungi was accomplished utilizing an Andersen N6 single-stage viable (microbial) particle sampler (Thermo Andersen, Atlanta, GA). The sampler is a cascade impactor with 400 precision holes, which provide a sharp cut off diameter of 0.65 µm. (18) Air was drawn through the sampler using a vacuum pump at a calibrated flow rate of 28.3 liters per minute (L/min). Sampling time for both indoor and outdoor samples ranged from three to five minutes, which provided a quantification limit of between 7 and 12 colony forming units per cubic meter of air (CFU/m 3 ). Prior to collecting each sample,