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Are UV Lights Effective In Killing Germs?

Yes, but on a static surface not moving air.


The use of UV lights has been around for more than 70 years. When UV light is shone on single-cell organisms it breaks down their DNA and deactivates it. Likewise, 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. For a single cell organism, like viruses, bacteria, and mold, it is immediately deactivated when coming into contact.


Different UV bandwidth for different applications. A bandwidth of 254nm of certain intensity can cause deactivation. UV intensity correlates to the time and the distance 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 HVAC coil to deactivate COVID virus before it gets back into the air doesn’t work on a regular system.


What is the UV light good for in the coil? 

It functions 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 HVAC system are isolated parts, such as Photocatalytic Oxidation (PCO) and Bipolar ionization (BPI) do not kill microorganisms directly but actively generate a catalyst and release them into the air to deactivate them. 


* Plasma Air uses the BPI technology. 

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