Ultraviolet Light Sanitizing and Coronavirus (COVID-19)
Does UV light kill COVID? Let us look into this together. Ultraviolet light in the “C” range, also called UVC, has been shown to kill SARS-CoV-2, the virus that causes COVID-19. However, the huge challenge with using UV-C light is being sure your UV lamp gives a sufficient dose of UVC light to all the surfaces you require to disinfect, such as a mask, phone, or an entire room, and that you are not exposed to the UVC light, as it is hazardous.
UVC works faster and most reliably on non-porous surfaces. However, it may be easier and faster and safer to clean such surfaces with liquid disinfectants. Consider using UV-C light to disinfect an object like using a hair blower to dry an object. Without a doubt, it can take a lot of time. On the other hand, with UV-C, you often won’t know when you’re done.
Many UV products marketed as having the ability of “killing 99.9% of germs” may be so weak that you would need to hold them for an hour at different angles to disinfect a mask. Masks can be more easily disinfected in other ways, such as in a washing machine (for cloth masks) or at low temperature in an oven (for N95 masks).
If you are still interested in using UV light to help protect yourself from coronavirus, here are the things you’ll need to know. Further below are our reviews and comparisons of UVC products marketed to consumers.
How UV Light Kills Germs
UV radiation kills viruses and bacteria by destroying their genetic material (DNA and RNA). Among the three main types of UV light, UVC, which has a wavelength range of 200 to 280 nm, is the most effective for inactivating viruses, with the most effective wavelength being about 260 nm.
To be effective, the right “dose” of UVC must be applied. The dose is a function of the UVC intensity or “irradiance” from a given distance from the object times the number of seconds the object is exposed.
Irradiance is measured in milliwatts (mW) per square centimeter (cm2), and the dose of UVC is measured using millijoules (mJ) per square centimeter (cm2) of the object being irradiated.
Therefore, if your UVC lamp has an irradiance of 5 mW/cm2 at a specified distance from an object, then holding the lamp at that distance from the object for 8 seconds will deliver a dose of 40 mJ/cm2, since 5 mW/cm2 multiplied by 8 seconds = 40 mWs/cm2 or 40 mJ/cm2. Generally, a dose of 40 mJ/ cm2 is considered sufficient to disinfect with a 99.9% reduction in infectivity, a wide range of bacteria and viruses, including certain coronaviruses that infect animals.