The inverse square law applies to germicidal ultraviolet as it does to light: the killing power decreases as the distance from the lamps increases. The average bacterium will be killed in ten seconds at a distance of six inches from the lamp in an American Ultraviolet Germicidal Fixture.
So, how much UV light is needed to kill bacteria?
The dosage, a product of UV light intensity and exposure time, is usually measured in microjoules per square centimeter, or equivalently as microwatt seconds per square centimeter (μW. s/cm2). Dosages for a 90% kill of most bacteria and viruses range from 2,000 to 8,000 μW. s/cm2.
One may also ask, how effective is UV sterilization?
The use of UV sterilization, or ultraviolet germicidal irradiation, has been found to be extremely effective. Sources of UV sterilization can kill over 99% of viruses, bacteria, and fungi in an extremely short amount of time.
Is UV light safe for humans?
UV Light That Is Safe for Humans but Bad for Bacteria and Viruses. The research team found that continuous low doses of far ultraviolet C (far-UVC) light can kill airborne flu viruses without harming human tissues.
How do you tell if UV sterilizer is working?
For most UV lamps, the elapsed time is about 9000 hours, or one year of continuous use. After this time, you may very well still see the blue glow. Again, that's more a sign that the lamp is still getting power and not an indication that your water is fully disinfected.