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.
