The idea of using UV-C light to kill the COVID-19 virus by disrupting its RNA has captured the imagination of many in the technical community. Unfortunately, important application details about factors such as necessary exposure time and intensity levels may be hard to discern, particularly for those who are new to the technology.
A complicating factor is that most light meters aren’t sensitive to UV-C wavelengths, making it tough to gauge the output of specific UV-C sources. And meters that work at the UV-C range are specialized instruments that can be pricey.
One problem in evaluating UV-C sources is that they usually carry power ratings based on their power consumption rather than their power output. For example, one rule of thumb for mercury lamp-type UV-C sources is that their actual 254-nm output is between 10 and 30% of their input rating because of heat losses and the inefficiency of the lamp ballast. Better quality, larger, high-power lamps typically reside at the higher end of the scale.