Illuminating Engineering Society position for Ultraviolet Air Disinfection Systems (1), in written publication in response to COVID-19 Pandemic (15 of April 2020):
“Upper-room GUV air disinfection is a primary means of safe and highly effective air disinfection, provided it is planned, installed, commissioned, and maintained according to current international standards. A knowledgeable consultant is recommended. Room air cleaners, disinfecting air through HEPA filters, in-duct UV lamps, or other methods seem attractive, but their clean-air delivery rate when converted to room ACH is often trivial—no more than 1 or 2 added ACH. GUV in-duct air disinfection is a secondary approach to treating any recirculated air”.
On the market right now, there are 3 systems for Air Disinfection through the use of Ultraviolet Light C of 254nm:
- Upper Room
- Filtration Columns + UV light
- In-duct UV lamps
To understand why Upper Room Ultraviolet Germicidal Irradiation is better than the other systems for air disinfection, first is necessary to see how UVC light works:
Ultraviolet C light, irradiated over a virus or bacteria, affects its DNA, inactivating microorganisms. It’s not just enough with irradiate, we must irradiate during a determined time in order to inactivate infectious agents. This is called Ultraviolet Dose, and any pathogen has its own dose to be inactivated and die. If we want to Disinfect the Air of a Room, we will have to apply UVC light during determined time to the whole room air volume
- LIGHTDIS Upper Room system provides Ultraviolet C light, directly to room’s air volume. Contaminated air with viruses and bacteria is rapidly disinfected, as this air exhaled, sneezed, coughed from an infected person has been heated by body temperature, being warmer than the rest of the room air. So the infectious air, warmer, rises up to ceiling entering the UVC light zone emitted by LIGHTDIS fixtures on the upper side of the room. Therefore Virus and Bacteria Inactivation is direct and very fast since they are expulsed to air by infected persons.
As the air is being disinfected, its temperature comes down and the air descends being breathable without microorganism for other persons present in the room. Upper Room studies in real hospital conditions reveal that Tuberculosis infections are reduced an 80% (2). A LIGHTDIS Upper Room Air Disinfection fixture avoids infections between persons.
The natural air room convective movement is produced naturally, and can be enhanced by mechanical ventilation (fans, air conditioners) increasing effectiveness. Thanks to this air movement pattern, all the room’s air volume is fully disinfected without noise, with people present and carrying out normal activity. Room’s air movement is slow enough to irradiate effective doses of UVC light against pathogens (SARS Coronavirus, Measles, Influenza, Chickenpox, Pneumonia, Tuberculosis, MERS….) and fast enough to inactivate airborne microorganisms, reducing infections between people.
- In reference to Filtration Columns + UV light, to get germicidal effectiveness they must incorporate a lamp which emits Ultraviolet C light. Any other kind of Ultraviolet light doesn’t have Germicidal Effect.
Filtration columns incorporate a particles filter. In order to disinfect the air, a fan suctions the air inside the column exposing it to UV light and taking it out by the other side. This air flows inside the column at speeds around 1.5 meters/second in professional equipments. Applying 50 Watts lamp power, that’s to say, doubling the power of a basic Upper Room, columns even not reach a quarter of the dose of an Upper Room for the same volume of air. Furthermore, an Upper Room apply UVC directly over the infectious air fraction because it flows directly to the Upper zone, however is very difficult that a column takes the infectious air fraction just by air suction.
Columns disinfect the air, but disinfection level is lower than in Upper Room. This happens because the air flowing through the column is shortly exposed to UVC light due to air speed, and therefore dose values are hardly on target. By the other hand a professional column recirculates air at 14 cubic meter/hour. Imagine, just a room of 6m length x 4 meters width x 3 meters height, in overall 72 cubic meters. So the column needs 5 hours to “theorically” get all the air volume through the system. This kind of system cannot reduce or avoid infections among people, as microorganisms will be active in room’s air for long periods. Even more, pathogen reduction will be low.
- In –Duct UVC lamp installation for air conditioning systems, also disinfects the air, but air exposure time to Ultraviolet C light are low with corresponding low dose, as air speed inside the duct is around 2,5 meter/second. Then, solution starts by installing several UVC lamps along great distances to increase exposure times with corresponding economic and energetic costs. In this kind of system, air volumes are enormous, so think for example about the air volume inside an airport terminal. Air disinfection systems which don’t irradiate directly the room’s air volume, despite disinfect the air in some degree, don’t reduce infections among people.
(1) IES Committee Report: Germicidal Ultraviolet (GUV) – Frequently Asked Questions. IES Standards Committee April 15, 2020 as a Transaction of the Illuminating Engineering Society. ISBN 978-0-87995-389-8
(2) Institutional Tuberculosis Transmission. Controlled Trial of Upper Room Ultraviolet Air Disinfection: A Basis for New Dosing Guidelines.
World Health Organization, Geneva, Switzerland
ORCID ID: 0000-0002-5323-3196 (E.A.N.).