Technical
USING UV LIGHT AS
DISINFECTANT - PART 2
By Laura Cowley PE , LEED BD + C , Lilian Rodriguez Fu IALD , LC , and Pieter de Bod Pr . Eng ., LEED BD + C
Ultraviolet light ( UV ) technology is a non-chemical approach to disinfection and has been used and researched for decades . This is continuation of Part 1 published in the November 2021 issue of the RACA Journal .
This paper investigates using UV-C for disinfection of room air and surfaces , and its ability to effectively inactivate airborne viruses like the SARS-COV2 responsible for the Covid-19 pandemic . The paper explores different lamp options , potential applications , and safety considerations when using UV-C light for disinfection .
MOBILE WHOLE-ROOM ( BARE LAMP ) UVGI UNITS Mobile whole-room ( bare lamp ) units can be used to supplement ( not replace ) standard physical surface disinfection procedures . In closed , unoccupied sections of hospitals , manual systems are moved from room to room to disinfect surfaces with UV-C lights facing in all directions . Autonomous systems are also available .
Surfaces with thick dust may render the disinfection treatment non-effective . It is important to note that any area in shadow will not receive the benefits of the UV-C radiation so spaces with many objects or non-uniform placement of the unit may create a false sense of surface disinfection coverage , though autonomous units may mitigate this risk due to their ability to move around and increase coverage .
Advantages :
• Suitable for all climates and ventilation conditions
• Achieves high levels of surface decontamination and be used to enhance terminal cleaning of patient rooms upon discharge
• Can be deployed throughout a facility for targeted disinfection .
Disadvantages :
• Potential occupational exposure
• Very expensive
• Requires staff training
• No method to benchmark output
• Possible material degradation .
Figure 7 : Manual mobile whole-room ( bare lamp ) unit .
HANDHELD SURFACE DISINFECTANT UNITS Handheld disinfecting products typically emit inadequate strength UV-C light to reliably disinfect surfaces . Waiving it over a surface for a few seconds does not provide reliable disinfection . Limited directions are included for handheld devices , and it is confusing as to only allow operation when facing down . Unless the mobile device has a safety switch to only allow it to operate when facing downward , there is a safety risk when the human eye is exposed to the UV-C light . Due to safety risks associated with accidental exposure to human skin and eye and the level of training for any individual to use , we do not recommend this method .
Figure 8 : Autonomous mobile whole-room ( bare lamp ) unit .
GERMICIDAL IRRADIATION DOSE For any UVGI application , the ability of UV-C to inactivate micro-organisms is a function of the UV dose . A key characteristic of germicidal lamps of any sort is the UV-C radiation dose .
www . hvacronline . co . za RACA Journal I January 2022 53