Technical
USING UV LIGHT AS DISINFECTANT - PART 1
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 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 .
UV radiation is a type of electromagnetic radiation , present in the range between visible light and X-rays ( refer Figure 1 ) and is divided into UV-A ( 315 nm to 400 nm ), UV-B ( 280 nm to 315 nm ), and UV-C ( 100 nm to 280 nm ). UV radiation is undetectable by the human eye but when it falls on certain materials it may cause them to fluoresce .
UV radiation is artificially created using UV lamps . A germicidal lamp is an electric light that produces UV-C light .
The practice of using UV-C to disinfect is called Germicidal UV ( GUV ). The use of Germicidal Ultraviolet ( GUV ) lamps and lamp systems to disinfect room air and air streams dates to about 1877 i when Arthur Downes and Thos Blunt discovered the ability of sunlight to prevent microbial growth , and the ability to show that the ability to inactivate microorganisms is dependent on the dose ( intensity x time ) and wavelength of radiation , and the sensitivity of the specific type of organism .
Early applications used UV light prior to antibiotics and vaccines , and were used for air-disinfection in schools , hospitals , and other public buildings .
In 1904 the first UV quarts lamps were invented , and it was discovered that the UV lamp can be used as an antiseptic or germicidal .
In 1922 Mr Matthew Luckiesh released a book on Ultraviolet Radiation . Matthew Luckiesh was a physicist and the director of General Electric ' s Lighting Research Laboratory .
In 1934 UV light was used to disinfect air to reduce measles in Philadelphia ( USA ) schools .
1985 - Rise in TB in the United State of America caused a renewed interested in the use of UV Germicidal Irradiation ( UVGI ).
It was realised that UV light cannot kill viruses , but only deactivate them .
The application of UV-C is becoming increasingly frequent as concerns about indoor air quality increase ii . UV-C is now used as an engineering control to interrupt the transmission of pathogenic organisms such as Mycobacterium tuberculosis ( TB ), influenza viruses , mould , and potential bioterrorism agents iii .
EFFECTIVENESS OF UV-A , UV-B AND UV-C FOR DISINFECTION UV-A and UV-B are generally not effective to inactivate viruses . However , UV-C is known to be effective in inactivating viruses and disinfecting surfaces iv , v , water vi and air vii by killing bacteria , mould spores and fungi .
UV Germicidal Irradiation ( UVGI ) is UV radiation at wavelengths between 100nm and 280nm . Germicidal lamps generate UV-C radiation inactivating microorganisms predominantly at 253.7 nm viii .
On a microscopic level , UV-C photons photo-chemically interact with the RNA and DNA molecules in a virus or
Figure 1 : Ultraviolet Spectrum
www . hvacronline . co . za RACA Journal I November 2021 45