July 20, 2021
When you buy an air purifier for your home or office, you're probably looking at the specifications closely. Is it a HEPA filter? What grade of HEPA is it? Does it have a good CADR? What features does it have?
These are all good questions. A high quality air purifier should have a high grade HEPA filter and a strong motor capable of moving a lot of air. But what about the particles that aren't captured, or are too small to be captured by a HEPA filter?
UVC (Ultraviolet-C) lights solve that problem. 254 nm wavelength UVC light is germicidal, meaning they are capable of inactivating microorganisms such as bacteria, viruses and protozoa. This quality makes UVC energy an effective, environmentally-friendly and chemical-free way to prevent microorganisms from replicating in any environment.
The high energy from short wavelength UVC light is absorbed by the cellular RNA and DNA, damaging nucleic acids and preventing microorganisms from infecting and reproducing. This absorption of UVC energy forms new bonds between nucleotides, creating double bonds or “dimers.” Dimerization of molecules, particularly thymine, is the most common type of damage incurred by UVC light in microorganisms. Formation of thymine dimers in the DNA of bacteria and viruses prevents replication and the ability to cause infection.
The evidence regarding the efficacy of UVC on SARS-CoV-2 is still evolving, however available research suggests that UVC germicidal radiation is effective in the inactivation of SARS-CoV-2 and other microbial pathogens.
In addition, 254nm UV-C disinfecting devices have been proven effective against harder-to-kill pathogens than SARS-Cov-2, such as C.difficile and MRSA found in healthcare settings, as multiple clinical studies published in peer-reviewed journals indicate.
In order to have effect in an air purification device, UVC light must be placed somewhere in the path of air flow. Different machines use different strategies to create a germicidal effect.
Some manufacturers accomplish this with mercury UVC lamps behind the filter. The upside of UVC lamps is that they tend to be very powerful, but use a lot of energy, need to be periodically replaced, and can emit harmful ozone gas. Yet other devices use UVC LEDs which, while not as powerful, never need to be replaced and do not emit any harmful gases.
UVC germicidal lights add an extra layer of air quality protection above and beyond what HEPA filters offer alone. Air purifiers that offer strong UVC often cost a bit of extra money over similar models, but are generally worth the extra cost in the long run. It is definitely something to consider when selecting an air purifier for your home.