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Heterotrophic bacteria in an air-handling system
1Department of Microbiology, University of Queensland, Brisbane, Australia.
Applied and Environmental Microbiology
|December 1, 1992
Summary
Even clean air-handling systems can harbor significant bacteria, primarily Blastobacter, on cooling coils and in water. This biofilm formation occurs despite the absence of reported building-related illnesses.
Area of Science:
- Microbiology
- Environmental Science
- Building Systems Engineering
Background:
- Air-handling systems (AHS) are critical for indoor air quality.
- Microbial contamination in AHS can impact occupant health.
- Understanding microbial communities in AHS is essential for system maintenance.
Purpose of the Study:
- To enumerate and identify heterotrophic bacteria in a well-maintained AHS.
- To investigate bacterial presence on structural surfaces, drain pan water, and airstream.
- To determine if a visually clean AHS harbors significant microbial populations.
Main Methods:
- Bacterial enumeration using heterotrophic plate counts on R2A medium.
- Identification of bacterial isolates to the genus level.
- Scanning electron microscopy (SEM) for biofilm visualization.
Main Results:
- High bacterial populations (10^5 to 10^7 CFU/cm² or mL) found on cooling coils, drain pans, and evaporative condensers.
- Blastobacter species identified as the dominant genus.
- SEM confirmed Blastobacter as a resident biofilm on cooling coil fins.
Conclusions:
- A well-maintained AHS can host substantial bacterial populations, primarily Blastobacter.
- Biofilm formation by Blastobacter occurs on cooling coil surfaces.
- The presence of these bacteria does not necessarily correlate with reported building-related illnesses.