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Microorganism contamination of HVAC humidification systems: case study.

Burkhart-JE; Stanevich-R; Kovak-B
Appl Occup Environ Hyg 1993 Dec; 8(12):1010-1014
A study was conducted to identify microorganism contamination in the heating, ventilation and air conditioning (HVAC) humidification system of a building. Only the portion of the study dealing with the water sampling of the systems was considered in this report. The building was located in a large metropolitan city, and contained 44 air handler units located in the sixth floor penthouse mechanical room and ten units located in the basement. Air washers and steam injection were the two methods used at this facility for humidification purposes. A water sample was collected from the reservoir pan of the humidification system of each selected HVAC unit. The results of the sampling indicated that gross contamination by microorganisms can exist in an HVAC system's humidification water reservoir. Once the system is contaminated, it may be very difficult to eliminate these microbes. Extensive cleaning of one HVAC unit was carried out, only to find that the levels of microbial contamination actually increased. The authors note that steam injection systems serve as a source of humidification but do not, as had been thought, serve to sterilize the system through their high temperatures. The authors suggest that the high rate of air flow through the baffle plates tends to keep them dry. Keeping plates dry eliminates one of the environments which encourage microbial growth.
NIOSH-Author; Indoor-air-pollution; Water-sampling; Comfort-zones; Environmental-contamination; Disease-vectors; Office-workers; Closed-building-syndrome; Air-treatment-equipment; Indoor-environmental-quality
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Applied Occupational and Environmental Hygiene