Are UV lights effective in killing germs?
Yes, but on a STATIC surface not so for moving air.
The usage of UV lights is not a new technology but has been around for more than 70 years. When UV light shines on single-cell organisms it breaks down their DNA and deactivates it. If you walk outside under the sun, the UV rays will kill your skin cells by breaking them down, but because you have a lot of skin cells you have enough to lose. But for a single cell organism, like viruses, bacteria, and mold, it is immediately deactivated when coming into contact.
The bandwidth of the UV light is crucial. A bandwidth of 254 nanometers given a certain amount of intensity to cause the deactivation. It is calculated as the dosage of CT value. CT value is the function of the UV intensity of the light source and the time of exposure, measured in microwatt seconds per square meter. Distance from the light source has a higher density of exposure. Viruses that collide straight onto the light bulb are dead like a bug on a zapper.
Bacteria and mold can survive on their own, but viruses cannot, they need a host.
How much of that UV dose do you need to kill bacteria, viruses, mold, etc.?
Based on published influenza cases, the suggested intensity usages to achieve a 90%, 99%, and 99.9% deactivation rate, require a 2700-microwatt second per square meter UV dose. Mathematically, to deactivate microorganisms in a non-static moving airflow, of 500 FPM, you need 3.5 seconds of light exposure (equivalent to 28 feet worth of light bulbs spread apart 2 feet) on the airflow at a 1-foot distance, like 14 bulbs. Hence, for the UV lights in your HV AC coil to deactivate COVID for your occupants before it gets back into the air again doesn’t work on a regular system.
What is the UV light good for in the coil? Is to keep your coil clean. A cleaner coil is more efficient. Shining UV light on moving air will not work, but on a static coil yes. UV lights in the HV AC system as isolated parts, such as PCO not to kill germs but to activate a catalyst to generate oxides and released them into the air to kill germs. Here, we introduce a new mechanism ‘Oxidization’ or “Bi-polar ionization’.