How do UV air purifiers clean the air?
The way UV-C light air purifiers work is quite simple. As discussed above, they are designed to use UV lamps that can potentially alter the DNA of microorganisms and inactivate or destroy them. Depending on the material of the emitter (e.g., phosphor or quartz,) this light may be blueish or may not be visible to the human eye. Usually, residential units use mercury lamps that emit UV-C light at a wavelength of 254 nm, according to the EPA.

UV light air purifiers are generally a combination of a forced air system and another filter (like a HEPA filter). As a result, the UV light of the air purifier acts together with other processes to clean the air. Ambient, in-house air is forced through the unit and ventilated through a chamber with bulbs emitting light within the UV-C frequency. The UV lamp is usually placed downstream of a filter in a portable air purifier. Various factors such as the type of UV lamp, humidity and temperature can affect its performance.

UV-C lamps used in UV-C germicidal purifiers are silent, and the glow of many, depending on the casing mounted around it, is invisible to the human eye. They are generally odorless. UV bulbs may need replacing on a yearly basis, depending on the make and model.

What is PM 2.5?
PM 2.5 refers to a category of particulate pollutant that is 2.5 microns or smaller in size. The average cross-section of a human hair is 50 microns. PM stands for “particulate matter.” The EPA and many health organizations categorize particulate matter by size because different size particles have different health effects. For instance, PM 10 particles (particles less than 10 microns in size) can irritate your nose and eyes, but fewer of these particles penetrate deep into your lungs, so they do not cause the same health problems that smaller micron particles can, although they do increase rates of respiratory disease.