There are many types of air purifiers (also known as air cleaners or air sanitisers) available on today’s market. They come in many different sizes, shapes, and prices, and they offer a wide variety of technologies and capabilities. You may have already come across devices that use ultraviolet (UVC) light to capture and destroy airborne viruses and bacteria. Is this sterilisation technology worth it? Is it safe? Read on to learn more about UV air purifiers below.

UV light technology

UV light is classified by wavelength and, as a result, is separated into three categories:

1. UVA (315-400 nanometres): UVA rays have the longest wavelength of all rays in the UV spectrum. Due to their longer wavelength, they have the highest potential to cause skin cancer as they can access the middle layers of the skin (the dermis) upon exposure. UVA rays are naturally transmitted from the sun through the Earth’s atmosphere. Most of the UV rays in which you come in contact every day are UVA. Sun creams are designed to protect you from the UVA and UVB rays of the sun.
   
   
2. UVB (280-315 nanometres): UVB rays have a shorter wavelength than UVA rays.  Since they have a shorter wavelength, they are only able to reach the outer layer of the skin (the epidermis). Some UVB rays are absorbed by the ozone layer surrounding the Earth.
   
   
3. UVC (100-280 nanometres): UVC rays have the shortest wavelength of rays in the UV spectrum. All UVC rays are blocked by the Earth’s ozone layer. The only way to which humans can be exposed to UVC rays is through artificial means: lamps, layers, or other devices. This is typically the type of UV radiation found in air cleaners².

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UVC rays

The reason for which UVC rays were chosen for use in air filtration and purification is due to the low risk they pose to human health but high capacity to destroy airborne viruses and bacteria. Since they have such short wavelengths compared to other UV rays, UVC rays are unable to penetrate deeply into the human skin. Therefore, the risk of negative health effects like cancer, cataracts, and permanent vision loss are considered to be very low. In addition, quality devices are designed not to let the rays escape from the device and avoid exposing the user, as is the case with Eoleaf air purifiers.

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UVC LED technology

UVC rays are commonly used in hospital settings due to their ability to inactivate microorganisms and pathogens (bacteria and viruses, including COVID-19).

When bacteria and viruses are exposed to UV light, the radiation is absorbed into their DNA and RNA. This causes an inability to replicate, transcribe, and translate in these microorganisms, leading to inactivation of viruses and bacterial cell death. These viruses and bacteria can then no longer reproduce and pose danger to human health³.

A huge advantage of UV sterilisation as a filtration method against pathogens is that it does not lead to bacterial resistance. It is effective against all forms of microbes, regardless of their type or size. The discovery of the UV sterilisation method also resulted in a Nobel Prize in 1905.

How do UVC air purifiers work?

UV light at a wavelength of 254 nanometres is most commonly used in UVC air cleaners for disinfection purposes. According to a study on germicidal capacity in the UV spectrum, it was determined that 99.99% of airborne viruses and bacteria are ‘killed’ when exposed to 40 mJ/cm2 of UV light at a wavelength of 254 nm³. However, despite what certain air purification companies may claim, UV sterilisation technologies do not directly sterilise the air. In order to rid the air completely of airborne pathogens, exposure to the UV rays must last for several minutes. An air cleaner’s air flow is simply too fast to allow for the sufficient duration of exposure time.

This is why, if one of your goals for purchasing an air cleaner is to fight against pathogens, it is recommended to purchase a UVC air purifier equipped with both a HEPA filter (high efficiency particulate air) and UV sterilisation technologies. Indeed, the combination of the two is much more effective: the fan draws in the polluted air so that the HEPA filter can capture the germs, and then the UV rays kill or inactivate the microbes trapped in the filter and sterilise the filter itself. In fact, a 2021 systematic review found that a HEPA filter used alongside UV sterilisation technologies is a very effective filtration method for removing bacteria and viruses from the air and reducing their transmission4. Remember: a filter that is declared ‘HEPA-type’ is not guaranteed the same filtration capacities as a true HEPA filter! True HEPA filters are certified and tested for their efficacy.

Safety measures to protect from radiation

Looking directly at UVC rays should always be avoided. Direct exposure of UVC rays to the skin or eyes can lead to burns and eye injuries (photokeratitis). These injuries, if they occur, usually resolve themselves after about a week, and they do not lead to any known long-term damage².

When a UVC air purifier is equipped with UV sterilisation technologies, the device’s housing and design generally ensures that UVC rays cannot escape. This is the case for all Eoleaf devices. UVC air cleaners have air vortex chambers with a special design that minimises UVC exposure. This keeps viruses and bacteria inside the device once they are pulled in for filtration.

Ozone

Some UVC air purifiers release ozone if they are not using UV rays at a wavelength of 254 nm or below. UV rays at this wavelength are not strong enough to break down O2 into O-. This is excellent news because ozone is dangerous for your health. As a result, all of Eoleaf’s devices are rated as ‘ozone-free’.

Nevertheless, it is important to note that even ‘ozone-free’-rated devices can emit ozone. The ozone-free designation is given to any device that emits 0.1 PPM or less of ozone (the level recommended by the World Health Organization). Based on third-party testing of our devices, it was found that our devices release trace amounts of ozone (0.01 PM). This is where the importance of combining multiple filtration technologies comes into play: although this amount is already negligible, any amount of ozone released would be automatically removed by our other 8-step filtration methods, namely our activated carbon filter and photocatalysis technologies.

The benefits of a UVC air purifier

Purchasing a UVC air cleaner can bring a myriad of benefits for those trying to control disease transmission (like COVID-19), especially when equipped with a HEPA filter. The filtration methods we use in our UVC air cleaners are safe for both humans and animals. They can help to reduce the risk of disease spread due to viruses and bacteria in many situations:

In everyday public settings

Whether at school, in nurseries, at supermarkets, at restaurants, or out and about town, we are constantly in contact with other people. In a post-COVID-19 world, we know how quickly and easily epidemics can turn into pandemics if we are not conscious of disease transmission. Installing a UVC air purifier in everyday public settings can help protect us from pathogens.

UVC air purifiers also containing HEPA filters are particularly effective at reducing the risk of infection spread in public places. They fight against proliferation of viruses and bacteria in the air, which is helpful during annual epidemics like flu season. They can also help protect us against wide scale disease spread. Air cleaners equipped with UVC technologies can even help to combat airborne mould spores!

In offices, waiting rooms, and medical settings

UVC air purifiers can be particularly helpful in places like offices, conference rooms, training and care centres, and/or hairdressing salons.

Medical settings where people are waiting to be treated by a doctor like at hospitals and in waiting rooms at a GP surgery pose high risk. Patients breathe in the same air as those who may be ill with transmissible diseases. This may also be problematic in patient rooms where the risk of nosocomial disease (diseases contracted in hospitals) is extreme.

A February 2022 study found that the presence of a UVC air cleaner also containing a HEPA filter can help significantly in lowering the risk of pathogen transmission. It reduces both airborne bacterial and viral load, as well as levels of bacteria and viruses found on surfaces⁵.

How to choose a UVC air purifier?

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Air cleaners are available in a variety of shapes, sizes, and designs with a variety of capabilities and options (see our catalogue). This can sometimes feel overwhelming when choosing the right model for you. Before purchasing your UVC air purifier, it is important to consider the following factors:

Placement

In which room do you plan to install your air purifier? Make sure that you choose a place where your device will be unobstructed: away from walls, out of corners, and not blocked by furniture. Air circulation is optimal if your device is placed in the middle of a room. It is ideal to purchase a device that is designed for easy movement. Eoleaf’s devices come equipped with handles and wheels, making it simple to move from room to room! Remember to always ventilate your room regardless of where you place your air cleaner.

Autonomy

UVC lamp lifespans can vary, but they generally are made to last about 10,000 to 20,000 hours before needing to be replaced. Depending on usage, they may last up to several years. It is ideal to leave your UVC air purifier running whenever the room is in use; for example, in medical office waiting rooms, it should be switched on during opening hours. If purchasing a device with a HEPA filter, high-quality filters typically need to be replaced once annually (like Eoleaf’s). Lower-quality filters will need to be replaced more often.

Performance and options

Air purifiers are designed to filter the air in a room of a given size. Contact the manufacturer of your air cleaner to ensure that you purchase a device that is properly sized to the room where you plan to install it.

Do not hesitate to reach out to our team of air purification experts with any questions you may have in finding the right device for you. We have also put together a detailed Buying Guide which can help you consider all of the factors involved in choosing an air purifier.

Resources

¹ Ultraviolet radiation measurements: UVA, UVB, UVC. Aktinovolia. (2020, December 15). https://aktinovolia.com/measurement-ultraviolet-radiations-uva-uvb-uvc/

² Center for Devices and Radiological Health. (2023). Ultraviolet (UV) radiation. U.S. Food and Drug Administration. Retrieved February 26, 2023, from https://www.fda.gov/radiation-emitting-products/tanning/ultraviolet-uv-radiation#3

³ Beck, S. E., Rodriguez, R. A., Hawkins, M. A., Hargy, T. M., Larason, T. C., & Linden, K. G. (2015). Comparison of UV-induced inactivation and RNA damage in MS2 phage across the germicidal UV spectrum. Applied and Environmental Microbiology, 82(5), 1468–1474. https://journals.asm.org/doi/10.1128/AEM.02773-15

⁴ MediLexicon International. (2021, October 27). UV air purifiers: Pros, cons, and effectiveness. Medical News Today. Retrieved February 26, 2023, from https://www.medicalnewstoday.com/articles/uv-air-purifier#how-effective-are-they

⁵ Arıkan, Genç, Uyar, C., Tokur, M. E., Balcı, C., & Perçin Renders, D. (2022). Effectiveness of air purifiers in Intensive Care Units: An intervention study. Journal of Hospital Infection, 120, 14–22. https://www.sciencedirect.com/science/article/pii/S019567012100373X