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Why do we need air disinfection? (1)

September 2, 2010 Leave a comment
Technologies for air disinfection
The most common air disinfection method is using ultraviolet (UV) radiation. UV radiation (UV-C) kills bacteria and viruses by damaging the DNA/RNA of the cells of microorganisms. However, UV radiation could only disinfect air close to the lamps as UV light has limited penetration capacity. In case of SARS contaminated room, UV disinfection alone is not adequate to provide virus-free environment for us.
Another well-known air cleaning method is to employ High Efficiency Particulate Air (HEPA) filter. HEPA filter can capture particulate sizes down to 0.3 microns, and so bacteria with size larger than 0.3 microns could be trapped in the filter. Although HEPA filters are effective in reducing airborne bacteria  in air, it is not effective to remove viruses, which are nanometer (10-9 m) in size. Also, air must pass through the filter in order for it to be cleaned. Hence HEPA filters can only clean air that is within a short distance of the HEPA unit. These drawbacks make HEPA filters become an unsatisfactory candidate for disinfection of SARS contaminated areas.
Chemical disinfectants could also be used for air disinfection, usually by means of vaporizing or spraying. However, these chemical disinfectants are usually difficult to decompose, leaving toxic chemical residues that are hazardous to human health.
Ozone is a well-known powerful oxidizer which could kill microorganisms effectively. Ozone applications in water and wastewater treatments are well-documented and it is widely used by most of the modern cities. Although studies for using ozone to disinfect air are relatively limited, experimental results (2,3) indicate that ozone could also be an effective air disinfectant as in water. For example, Kowalski et al (2) investigated the bactericidal effects of high ozone concentrations on E. coli and S. aureus and concluded that more than 99.99% death rate was achieved for both species after ozonation.
In addition to the strong oxidizing power of ozone, properties of ozone also help it to be an ideal aerial disinfectant. In contrast to UV radiation and HEPA filter, ozone is a gas that could penetrate to every corners of the room, thus it could disinfect the entire room effectively. As ozone is unstable, it is readily converted back to oxygen, leaving no harmful residual ozone after disinfection.
Although ozone is success as an aerial disinfectant in laboratory experiments (1), its effectiveness in real situation needs to be further explored. In this article, the effectiveness of ozone in disinfection of a conference room will be evaluated and discussed.

 

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