Most air purifiers do not use HEPA filters due to cost and flow restriction caused by these higher performing filters. While standard non-HEPA filters provide help with things like dust and pet dander, they do not provide much if any protection from airborne germs. Some of these products add UVC light – typically by adding a low powered mercury bulb. The UVC intensity and residence time of the germs do not lead to any meaningful dose and germs that make it through the filter will not be killed at a high rate, meaning the germs will blow back out into your space with a new opportunity to infect you.
Some products have an ‘ionization’ process that puts charged particles out into the air which can attach to and eliminate particles and germs in the air. This can be found in both stand-alone air cleaning products and HVAC integrated products. The most common ions utilized in this technology are Hydroxyl and Hydrogen Peroxide, which are both found to be hazardous to human health
https://ucanr.edu/sites/superfund/files/142534.pdfThese ions are neutralized very quickly in the air, and while they can perform well in small testing chambers, they fail to provide safety as room size increases. Cost is generally high for these devices. When holistically considering human health, putting additional chemicals into the air in your space is not going to be the best solution.
Plasma: Plasma-based solutions have been shown to kill germs effectively. However, the process requires expensive materials and components, leading to an exceedingly high product cost and operating costs to achieve these results. UVC light, when used properly, can meet and exceed the results produced by plasma at a much lower cost to the customer.
Photocatalytic oxidation and photoelectrochemical oxidation are technologies used by some air purification technologies to kill airborne germs. These products use low energy UV light to activate a photocatalytic process, typically on the surface of their filter, in which ions are formed that can destroy germs. When tested, these products typically underperform when compared to basic HEPA filtering products – primarily because they process air slowly for the process to work. This limits germicidal results for a whole room. UVC + HEPA provides a much more effective whole room solution over PCO/PECO based products.