VENTILATION
Investigating the benefits of UV airstream disinfection
In an article that first appeared in the Institute of Healthcare Engineering, Australia’s magazine, Healthcare Facilities, Gregor Riese of the Opira Group discusses the effectiveness of ultraviolet airstream disinfection in hospitals and other healthcare facilities. He draws on a recent year-long study at a hospital in Pennsylvania which demonstrated a more than 90% reduction in airborne and surface pathogen levels in UV-treated zones compared with non-UV treated zones.
Figure 1: Installation of an in-duct UVGI system.
Real-world evidence for the impact of ultraviolet (UV) disinfection of moving airstreams on pathogens, and the demonstrated health benefits for building occupants, is slowly accumulating in scientific literature. Unlike ultraviolet germicidal irradiation (UVGI) targeting surfaces on cooling coils, hospital wards, or upper UV air disinfection, very few case studies on the impact of UVGI on air quality and health outcomes have been reported to date. Such information is important for building owners and facility managers considering airstream disinfection, particularly with the advent of the COVID pandemic, and heightened awareness of the potential of disease spread within indoor spaces via aerosols.
‘‘
Figure 2: A view of UVGI lamps mounted within the return air duct.
What is UV airstream disinfection? Ultraviolet airstream disinfection involves the installation of UV lamps to irradiate moving air within the mechanical air systems of buildings. Laboratory studies have shown that sufficient UV doses applied to moving air are effective in killing most infectious diseases spread by air transmission in healthcare settings. A typical UV air disinfection installation is shown in Figures 1-2, where the air in the return air duct is treated with UV to kill pathogens. Figure 3 shows an operating lamp, and Figure 4 a schematic diagram of the UV airstream disinfection process. UV airstream disinfection systems
are typically sized to permit adequate irradiation dosage of the air stream, calculated as a function of duct size and air speed. This UVGI dosage, expressed
Ultraviolet airstream disinfection involves the installation of UV lamps to irradiate moving air within the mechanical air systems of buildings. Laboratory studies have shown that sufficient UV doses applied to moving air are effective in killing infectious diseases
in Joules per centimetre squared (J/cm2
is proportional to the product of the UV source power per unit area expressed in Watts per square metre (W/m2
), ), and the
exposure time in seconds. Consequently, the power requirements for these installations are far higher than surface disinfection given the very short residence time of air passing the UV lamps. The exposure time of moving air to obtain the necessary dose can be as little as half a second on a single pass, depending on the air speed and size of the UV lamps within the duct.
Proprietary software Companies installing UV airstream disinfection systems currently use proprietary software to size the lamp installation appropriately. These often allow selection of specific infectious disease, such as a Tuberculosis, Influenza A, and SARs-CoV-2, with each having different exposure tolerances for UV light (measured as LD90). Moulds and spores can also be targeted by UV air disinfection, but are far less susceptible to UV, and require multiple passes through the system before they are sterilised.
August 2022 Health Estate Journal 23
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72
