I looked into implementing this once. Some surprising things I learned:
1. You need UV-C (typically 222 nm), not just any old UV bulb off Alibaba/Wish/Amazon.
2. You need an extremely high UV light intensity to kill viruses if the air is just flowing past the bulb (vs shining UV on a coil to prevent bacterial/fungal growth, which is the typical usage), and you need more intensity the faster the air is flowing. Usually this requires multiple bulbs.
3. You need to replace your UV-C bulbs every 1,000 hours or so, because they rapidly lose intensity with operating time.
Just putting a "black light poster" bulb in your ducts won't accomplish anything, other than perhaps giving you a false sense of security.
> You need to replace your UV-C bulbs every 1,000 hours or so
I don't think this should need to be the case. Low pressure mercury arc lamps (253.7nm) last 10,000 hours in water treatment applications - a much more palatable replacement timeline (1 year) vs every few weeks!
The short-lifetime bulbs are usually 222nm Far-UVC bulbs, which are safe for human exposure. These shouldn't be necessary to treat air as part of an enclosed HVAC system. I feel that the hype around 222nm / "safe" UVC has done a disservice to just using "dirty" 253nm UVC, which kills everything just as well as long as you keep people from being able to look at it.
Thanks for the correction. It's been a while since I looked into it!
Even replacing bulbs every 1 year seems like a lot more than people are bargaining for. Most people seem to expect UV will be a "Set It And Forget It" solution (hence why they prefer it over filters), so they risk neglecting the necessary replacement interval.
1. You need UV-C (typically 222 nm), not just any old UV bulb off Alibaba/Wish/Amazon.
2. You need an extremely high UV light intensity to kill viruses if the air is just flowing past the bulb (vs shining UV on a coil to prevent bacterial/fungal growth, which is the typical usage), and you need more intensity the faster the air is flowing. Usually this requires multiple bulbs.
3. You need to replace your UV-C bulbs every 1,000 hours or so, because they rapidly lose intensity with operating time.
Just putting a "black light poster" bulb in your ducts won't accomplish anything, other than perhaps giving you a false sense of security.