Safer air needs proven technology
Don't fall prey to misleading claims - proven methods of HEPA filtration and ventilation can reduce viral risk as part of a multilayered approach
Improving indoor air quality can reduce COVID risks as part of a multilayered approach,1 along with masking (N95 or better respirators), up-to-date vaccination, physical distancing, and other proven approaches.
Two basic approaches to reducing pollutants in indoor air are ventilation and filtration. Ventilation options include opening windows (when weather and outdoor air quality permit) and enhancing HVAC systems to increase air changes per hour. Filtration options include upgrading filters on HVAC systems (MERV 13 or higher, if possible) and adding portable HEPA air purifiers.
I have portable HEPA air purifiers in every room of my house as well as on my office desk on campus, and most of them were around $100 each. Along with masking and other multilayered protections, HEPA air purifiers are useful for reducing the risk of COVID, as well as for reducing allergens and particulate components of pollution and wildfire smoke (such as PM2.52).
When you purchase HEPA air purifiers, be aware that the use of the term “HEPA” is unfortunately not standardized. Look for the terms “True HEPA,” “H13,” or “99.97% filtration” to ensure that you are getting a high filtration product. Look for established brands, and buy only name-brand replacement filters. If there is a “plasma” or “ionizing” feature, ensure that it can be turned off, as such features do not have proven effectiveness and can produce ozone and other toxic byproducts.
Industrial hygienist Fran Gilmore has written two excellent guides that I highly recommend checking out for further reading on ventilation: Ventilation for Coronavirus in the Workplace3 and Ventilation for Coronavirus in Schools.4
Unfortunately, unproven technologies have flourished in an environment where those who care about stopping the spread of COVID are left without appropriate support from public health authorities, governments, and other trusted leaders. Online groups and social media spaces across many platforms are being used to market these unproven technologies, and mentions are even creeping into COVID advocacy documents.
The CDC has some excellent advice regarding emerging technologies for air cleaning:5
CDC recommends using technologies that are known to work and will not cause harm. Be cautious when considering an emerging new technology. Do your homework, to include requesting proof of performance and safety under real-world, as-used conditions.
From CDC’s Ventilation in Buildings > Ventilation Frequently Asked Questions #8
Ultraviolet light is one approach that has the potential to kill infectious organisms but poses dangers that must be avoided. UV radiation can be divided into three types based on the wavelength of the light—UVA (315-399 nm), UVB (280-314 nm), and UVC (100-279 nm). All three types of ultraviolet pose health risks, although the specific type of damage varies based on the energy and depth of penetration of the UV rays. UVA has the deepest penetration, while UVB has an intermediate depth of penetration—both of these can impact the skin and eyes. These types are usually associated with sunburn, premature aging, skin cancer, and cataract formation. This is why we wear sunscreen, protective clothing, and sunglasses that protect our skin and eyes from UV when out in the sun. UVC from the sun is absorbed by the ozone layer and atmosphere, so in sun exposure we are primarily exposed to UVA and UVB. UVC is the highest energy portion of the UV spectrum, and people are only exposed by artificial sources (such as welding torches, tanning booths, or germicidal lamps discussed below), which can be damaging without appropriate precautions.6
Germicidal UVC (centered at 254 nm) is an established technology used in a variety of workplace settings such as laboratories and hospitals. Germicidal UVC must be professionally installed to ensure safety and efficacy. Germicidal UVC is used in unoccupied spaces predominantly for disinfection of surfaces or in fixtures that block the UV rays from reaching people (as in upper-room germicidal UV irradiation7) to ensure that people are not exposed. Germicidal UVC use has the potential to produce ozone and other toxic byproducts,8 so this is an important consideration for this approach that is not a concern with ventilation and HEPA filtration. Germicidal UVC is not appropriate for general home use.
UVC can cause severe skin and eye burns (corneal damage known as photokeratitis) with unprotected exposure. On the SUNY Geneseo campus in January 2022, UVC lamps were installed in classrooms in an attempt to reduced COVID risks. The UVC lamps were inappropriately installed with the UV light source visibly exposed, causing skin and eye burns for multiple faculty members.9 Given the above considerations, any exposed UV light source should be considered unsafe and should be avoided.
Far-UVC is an emerging technology that uses light centered at 222 nm. This approach has been promoted with insufficiently supported claims that the 222 nm wavelength of UV light is safe for human exposure while inactivating viral particles. Far-UVC devices do NOT have well-established safety or efficacy. Long term follow up is particularly limited in existing studies of the safety of Far-UVC. It is also difficult to know what wavelengths of UV light are being emitted by a device unless a company publishes their spectral power distribution.10 (It is impossible, by the laws of physics, to emit light “only” at a single wavelength.)
Don’t waste your money on Far-UVC devices—buy a HEPA air purifier or a better respirator instead. Here is my list of questions that I would need suitably answered before considering use of Far-UVC technology in any setting:
How can a consumer tell that the device is working?
How can a consumer tell that the device is safe?
Is the device approved by the EPA or any other government agency pertaining to safety and efficacy?
What organizations certify the safety and efficacy of the device?
What professional medical or public health organizations have endorsed the device?
What is the spectral power distribution (how much light is emitted at various wavelengths) of the device? How can a consumer verify the power of light emitted at 222 nm (Far-UVC) compared to the power of light emitted at other wavelengths?
How does the safety and efficacy of the device change over time?
Are ozone or other toxic byproducts generated during use (from the interaction of Far-UVC light and materials in the room) that would impact indoor air quality?
How can consumers be sure they are not receiving a counterfeit device?
Provide the peer-reviewed publications detailing the research data regarding the safety of the device regarding eye exposure (corneal damage and cataract development) and skin damage (sunburn and skin cancer risk). Have the results been independently verified in multiple, large-scale clinical trials? What was the length of follow up?
So far, none of the devices I have come across pass muster.
Thank you for taking the time to learn how to avoid unintentionally spreading misinformation or unproven marketing claims about air cleaning. Anyone can fall for spreading what looks like news of something exciting or hopeful, regardless of background or education. We need to stay vigilant to avoid being misled. Ventilation and HEPA filtration are proven approaches that can be used widely to reduce the risk of spreading COVID. If you found this information helpful, I encourage you to share it wherever it may reach people who may be interested.
Stay safe, my precautionary friends! 😷
https://www.acs.org/pressroom/presspacs/2022/acs-presspac-december-2022/germicidal-uv-lamps.html
Peng Z, Miller SL, Jimenez JL. Model Evaluation of Secondary Chemistry due to Disinfection of Indoor Air with Germicidal Ultraviolet Lamps. Environ Sci Technol Lett. 2023;10(1):6-13. doi:10.1021/acs.estlett.2c00599