Azure - - Spot­light - How do we fight some­thing we can’t see?

Since the on­set of COVID-19, in­vis­i­ble air­borne viruses and bac­te­ria have been at the fore­front of ev­ery­one’s minds. As a re­sult, in­creased san­i­ta­tion and dis­in­fec­tion pro­to­cols have been im­ple­mented across the board. One strat­egy that’s gar­ner­ing a lot of re­newed at­ten­tion? UV light.

For more than 100 years, en­gi­neers and de­sign­ers have been har­ness­ing the power of ul­tra­vi­o­let ra­di­a­tion to kill off pathogens. And though it’s a sur­pris­ingly old idea (first dis­cov­ered by Jo­hann Wil­helm Ritter in 1801, well be­fore an­tibi­otics), UV is now gain­ing real trac­tion as yet an­other line of de­fence.

“Ul­tra­vi­o­let ra­di­a­tion de­grades and de­com­poses DNA, which is very ef­fec­tive in deal­ing with bac­te­ria, and makes RNA in­ac­tive, which is very ef­fec­tive against viruses like COVID-19,” says Rafael Cor­rea, senior as­so­ciate at the Toronto of­fice of con­sult­ing en­gi­neer­ing firm Smith + An­der­sen. “UV is di­vided into three bands: UVA and UVB, which are more harm­ful for hu­mans, and UVC, what we call ger­mi­ci­dal UV or GUV, a dis­in­fec­tion method that uses this wave­length.” In na­ture, UVC is blocked by ozone.

For the pur­poses of san­i­ti­za­tion, the ap­pli­ca­tions and uses of ger­mi­ci­dal UV need to be care­fully con­sid­ered. “It’s not some­thing you can just im­ple­ment in a build­ing, leave on and for­get about,” says Cor­rea.

“It can be very harm­ful, es­pe­cially at close dis­tances. You need to have safety pro­to­cols and staff train­ing, and to avoid di­rect con­tact with hu­man eyes and skin.”

The teams at Smith + An­der­sen adopt a prag­matic ap­proach when in­te­grat­ing the tech­nol­ogy into their schemes. “You have to weigh the pros and cons as it re­lates to the ap­pli­ca­tion, talk to the client and fig­ure out what they are try­ing to achieve,” says prin­ci­pal Si­mon Aspin­wall. “The use of UV is most ap­pli­ca­ble in health­care set­tings due to the many hos­pi­tal-borne in­fec­tions that don’t gen­er­ally oc­cur else­where in so­ci­ety; its use is se­lec­tive and ap­plied in a com­bi­na­tion of per­ma­nent (such as pa­tient wash­rooms) and por­ta­ble sys­tems to treat a va­ri­ety of room types.”

Gen­er­ally speak­ing, the sci­ence be­hind the use of UV is sound, and it’s proven to be nearly 100 per cent ef­fec­tive in a con­trolled set­ting. “It’s about in­ten­sity and du­ra­tion,” says Aspin­wall. “If you have a UV light over­top a petri dish in a lab, it will kill the or­gan­isms within it. It’s ef­fec­tive from that per­spec­tive, but it’s the ap­pli­ca­tion that’s the chal­lenge. The prob­lem with UV is that it only kills what you can see. It’s a di­rect line of sight.” De­sign, there­fore, is key. “Once you start to add real-life sit­u­a­tions, such as par­ti­tions that cre­ate shadows, the de­signer needs to ac­count for that,” says Cor­rea. “We al­most need to have the fur­ni­ture plan in the be­gin­ning stages, so the light­ing can be ef­fec­tive to dis­in­fect the en­tire area.” Be­cause the sys­tems could in­deed de­grade other ma­te­ri­als such as plas­tics, in­ten­sity and du­ra­tion are con­se­quently of­ten lim­ited. At lower lev­els, it could take six to 24 hours to com­pletely dis­in­fect a space; at a higher level, that time goes down dra­mat­i­cally.

There are three main ar­eas in which UV ap­pli­ca­tions can be used ef­fec­tively, the first be­ing HVAC and other me­chan­i­cal sys­tems. These safe, en­closed sys­tems kill mould on coils, and can help to dis­in­fect the air if the strength of the light is in­creased. “It’s about the quan­tity of lamps, their in­ten­sity and the ex­po­sure time,” says Aspin­wall. “It might take mul­ti­ple passes to dis­in­fect the air, de­pend­ing on the de­sign of the sys­tem and what you are dis­in­fect­ing.” A sec­ond use is up­per-room UV sys­tems that point to the ceil­ing and are left run­ning. “These sys­tems are used and have been stud­ied in coun­tries where air­borne dis­eases are more preva­lent,” says Aspin­wall. The last ap­pli­ca­tion is what is known as dis­in­fec­tion UV, used in un­oc­cu­pied spa­ces. These can be por­ta­ble sys­tems that are wheeled into a room and left on for five to 10 minutes to ir­ra­di­ate sur­faces.

An­other fac­tor to con­sider is the cost — of the en­ergy to run the units, clean­ing and main­te­nance, bulb re­place­ment ev­ery one to two years. The lamps also aren’t suit­able stand-ins for stan­dard clean­ing pro­to­cols and should be seen as sup­ple­men­ta­tion.

In other words, GUV sys­tems are highly ef­fec­tive and quickly gain­ing ap­peal, but are very much cas­espe­cific. And while not ev­ery­one is jump­ing on the UV train right away, says Aspin­wall, more clients are ask­ing ques­tions about it. smithan­dan­der­

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