:: Section 7 of 10
Indoor air quality is a significant concern to professionals in the bioaerosol field. Office buildings, hospitals, dormitories, airplanes, and similar climate-controlled structures that rely largely on re-circulated air sustain abnormally large numbers of viable bioaerosols, often including pathogenic bioaerosols.
There are certain natural inactivation mechanisms for microorganisms that are very effective. Sunlight and natural oxidants (e.g. ozone and free radicals) in the ambient air can inactivate them, and many microorganisms do not survive well in low relative humidity. However, ductwork provides airborne microorganisms with a moist environment, protected from sunlight and free radicals, thereby eliminating the most effective means of inactivation. Once a pathogenic bioaerosol is released indoors, the ductwork can preserve it. The central air system then distributes them to the entire structure, spreading the pathogens incredibly effectively and exposing numerous people as a result (see animation below). Therefore, the threat of pathogenic bioaerosols are especially potent in indoor scenarios.
Indoor air quality is especially a concern in hospitals, where airborne pathogens are common. Infections that are acquired while in the hospital are known as nosocomial infections. Approximately 2.5 million hospital patients each year acquire nosocomial infections12, prompting hospitals to take a serious look at how to minimize the problems. One response of collective protection has been to provide duct work with UV light to inactivate the airborne pathogens.
Figure 11: Central air systems can protect and distribute bioaerosols.
12Chapter 4, Wastewater Microbiology, Bitton, 2005