UV Part 2 – Honest UV Facts from a Manufacturer
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As with other IAQ products like PCO products, UV lights can be used well but are often misapplied. Ozone generators, including PCO products, are oxidizers that bind to contaminants and neutralize them. However, oxidizers can also affect bodily tissues when misapplied.
Some UV lights produce ozone, and others don’t. UV wavelengths are on a spectrum (a smaller area of the electromagnetic spectrum), and germicidal UVC peaks at 254 nanometers; ozone production happens beyond 185 nanometers. UV wavelengths are typically between 185 and around 400 nanometers. UV lights also damage eye and skin tissues, so you need to use the appropriate PPE when working with them.
UV germicidal lamps are typically appropriate for killing microbes on surfaces. However, there are also airstream kill rates. UV may be effective against SARS-CoV-2 in a plenum, even though viruses aren’t “alive” and don’t grow on coils or surfaces. Therefore, claims that UV lights kill SARS-CoV-2 are likely to be misleading, and we would need more data to support claims.
Some rumors have been going around that the CDC has given SARS-CoV-2 samples to IAQ manufacturers, but that is certainly NOT happening. Extreme precautions are being taken, and even though scientists are still actively researching the virus, it isn’t safe or responsible to provide samples to manufacturers.
Viral transmission is also more probable from contact with surfaces, so it doesn’t make a lot of sense to focus on killing it on surfaces that we don’t touch (coils) or in the airstream of the HVAC unit. Bulb intensity also fades over time, even though they may still appear to be lit. As a result, it’s best to replace bulbs according to the manufacturer’s recommendation.
UV lights need to be used with caution, though higher-microwatt UV lights might come with disclaimers that the coil or drain pan could be damaged by the UV. However, Ron has yet to receive complaints about broken drain pans due to UV lighting. LED technology is starting to be used with UV lighting, though we don’t really use it in central A/C. However, some commercial refrigeration and ice machine applications are better candidates for that technology.
When we use PCO technologies or hydroxyl radicals, we have to consider that those could cause incomplete degradation when they interact with surfaces (like flex duct lining and filters) and VOCs. Activated carbon can help absorb chemicals and odors without the same effects as ozone-based technologies. Photocatalytic oxidation technologies also have only independent testing (no third-party peer-reviewed studies) and no EPA testing standards, which contribute to stigmas against those technologies.
Even with all of the IAQ products we have, handwashing and disinfecting surfaces with bleach will be some of the best protective measures you can take during the pandemic.
Ron and Bryan also discuss:
The history of Fresh-Aire UV
The relationship between time, intensity, and distance of UV lighting
Whole-room irradiation strategies
UV lights and mirrors or reflective materials
The ethics behind the claim that “UV kills SARS-CoV-2”
Handheld UV technologies
PCO products and pressure drops
UV on the inlet vs. outlet side of the evaporator