Danny as been writing about air purifiers for 10+ years. He is a major fan of home technology, which makes him the perfect person to test and evaluate products for HouseFresh
The onset of COVID-19 has had a drastic effect on all of our lives. Not only has this deadly virus changed the way we live, work, and interact with others, it has also led to a worldwide focus on what we could do to remove it from our environment.
At the beginning of the pandemic, American families were advised to start disinfecting groceries, washing their clothes more regularly, and cleaning door handles after each touch, all to avoid surface transmission. But research later found that surfaces were an unlikely route of transmission for most people.
As we learned more about the virus, many studies concluded that airborne transmission was the main way that SARS-CoV-2 spread. So this became the primary focus for air purifier companies to show how their products could kill and remove the virus from the air.
It’s worth noting that the main ways to stop this airborne transmission of SARS-CoV-2 is through masks, social distancing, and opening windows but the CDC also recommends the use of HEPA air purifiers to remove virus particles from the air.
The evidence for HEPA-based air purifiers is pretty conclusive for a technology that was first invented during World War II and is very effective at removing viruses from the air.
While HEPA is great for removing virus particles from the air, it will not directly kill viruses, and there is the potential for these viruses to get back into the air.
What is UV-C
Using UV to clean air, like HEPA, is not a recent technology. Back in the 1930s, it was used in Philadelphia schools to keep the air clean to control the spread of measles.
UV-C is a type of ultraviolet light with a shorter wavelength than visible light but longer than X-Rays. UV-B is the wavelength many people will recognize as this is what causes sunburn and potentially skin cancer.
UV-C wavelength (254nm) is extremely damaging to any living creature, including viruses, as it directly damages the DNA molecules and so is perfect for killing viruses like SARS-CoV-2.
This is one of the reasons that UV-C-based devices are used to sterilize operating equipment in hospitals.
The current advice from the CDC is that they support using upper-room UVGI devices to help kill viruses in the air of a room. However, these units are custom fitted by an HVAC professional and cost around $2000 per 500ft2, so are very different from the portable units that include a small UV-C bulb. These units are used above where people move to avoid direct exposure of to UV people in the room.
The Problem with UV-C Air Purifiers
While the science supports that UV-C can effectively kill viruses, it isn’t a magic bullet, as the waves need enough time to interact with the virus particles, which can be blocked by dust or other particles in the air. This is why hospital units take upwards of 30 minutes to sterilize devices in a biosafety cabinet. Most studies on UV-C air purifiers were done under strict conditions that are unlike the situation for most consumers.
Many air purifier manufacturers are adding UV-C light bulbs to existing HEPA units. We would question their effectiveness and worry about the potential for direct exposure to UV to the humans in the room.
Should You Get a UV-C Air Purifier?
UV-C will be a key part of the fight against viruses in the future, but the evidence is still not clear enough to support their usefulness in portable air purifiers.
A quick look on Amazon.com shows that UV-C has become the latest jargon to sell specific air purifiers, but I would be wary of most of the units that employ this technology. Many of these units will use UV-C lamps that are not powerful enough to affect viruses in the air significantly.
It doesn’t mean that UV-C is something we will ignore, there likely will be consumer units that provide value, but right now, we would recommend going with a HEPA-based unit as they have been proven in numerous peer-reviewed publications to remove viruses and other particles from the air and have no potential adverse side effects.
Be sure to check what air purifier for viruses we recommend as of 2023 based on our internal tests and evaluation.
Sources:
Ten scientific reasons in support of airborne transmission of SARS-CoV-2 (2021). The Lancet. thelancet.com
Indoor Air in Homes and Coronavirus (COVID-19) (2021). EPA. epa.gov
Improving Ventilation in Your Home (2021). CDC. cdc.gov
COVID-19 rarely spreads through surfaces. So why are we still deep cleaning? (2021). nature. nature.com
THE ENVIRONMENTAL CONTROL OF EPIDEMIC CONTAGION (1941). GHD Center Harvard. ghdcenter.hms.harvard.edu
Removal of SARS-CoV-2 bioaerosols using ultraviolet air filtration (2021). Cambridge University Press. cambridge.org
Upper-Room Ultraviolet Germicidal Irradiation (UVGI) (2021). CDC. cdc.gov
COVID-19 Outbreak and Hospital Air Quality: A Systematic Review of Evidence on Air Filtration and Recirculation (2020). ACS Publications. pubs.acs.org