Air purifiers are common air treatment devices used in Australia to remove allergens in indoor air such as dust, pet fur, and pollen. Due to rising concerns about virus and bacteria transmission indoors, consumers have taken into account the ability of air purifiers in destroying germs when choosing a suitable air purifier for their homes. Among various germicidal technologies used in air purifiers, UV light has proven to be one of the efficient technologies for inactivating bacteria and viruses in the air.
The UV light used in air purifiers
Found naturally in sunlight, UV radiation may be classified into 3 types, namely UV-A, UV-B, and UV-C. This distinction is made based on their wavelengths. The ozone layer of the Earth absorbs all UV-C radiation and most of the UV-B radiation, but UV-A radiation reaches the Earth's surface all year long.
The type of UV radiation used in air purifiers is UV-C radiation, which has a wavelength of 100-279nm. Even though UV-C radiation in air purifiers is created artificially using UV light, it has similar properties to the UV-C radiation coming from the Sun. UV-C radiation has been used for decades in the medical field to reduce the spread of bacteria, such as tuberculosis. UV-C lights are also known as germicidal lights.
How does UV light disinfect the air passing through air purifiers?
UV-C radiation in an air purifier does not escape the confines of the air purifier to disinfect the surrounding air. Instead, it is safely contained within the air purifier to disinfect only the air that passes through the air purifier.
To disinfect the air, UV-C radiation damages the DNA of bacteria and viruses, and even mould spores, when they are exposed to the radiation for a period of time. The damage inflicted on the DNA disables these bacteria and viruses from carrying out their normal functions; subsequently, they lose their infectivity and die. However, this is not an immediate process—it can take up to a few minutes of direct exposure to completely inactivate bacteria and viruses.
This is where a good quality HEPA filter comes in handy. Having HEPA filters installed in UV air purifiers serves the essential purpose of trapping bacteria and viruses that are as small as 0.3μm, which in turn gives the UV radiation enough time to inactivate these trapped germs. UV lights greatly reduce the chances of reintroducing bacteria and viruses into the air when you open up the air purifier to change the filter. The lack of a HEPA filter in an air purifier greatly reduces its ability to disinfect the air.
Risks of using a UV air purifier
Much like ionisers, the use of UV light in an air purifier raises some concerns about its impact on human health.
Exposure of UV-C radiation towards skin or eye
Due to its ability to destroy DNA, direct skin or eye exposure to UV-C radiation can cause direct harm. Therefore, several precautions should be taken when using a UV air purifier:
- Make sure that the air purifier casing is securely closed, without any opening that exposes its UV light.
- Make sure that the air purifier is not running when you open up its casing for filter changes or cleaning.
- Make sure that the UV light is used only in the air purifier and is not detached and used elsewhere.
Generation of ozone
While the ozone layer in the atmosphere absorbs harmful UV-C radiation, it can cause health issues when it exists in the air at ground level. UV radiation is known to generate ozone as it reacts with oxygen in the air. That said, advances in technology have yielded forms of UV light that do not generate ozone at all. Many UV air purifier manufacturers conduct ozone level testing to make sure that ozone generation is kept at minimum levels.
While UV light is not a standard application in an air purifier, it is recommended for use in hospital wards or when someone is sick at home. Used together with a good HEPA filter, it provides an additional means of protection against the transmission of bacteria and viruses in the air. It is completely safe to use a UV air purifier when it is used in accordance with the instructions provided by the manufacturer.
Disclaimer: The information provided in this article is for general reference only. Please seek advice from professionals according to your needs.