You can buy HEPA units that have a strip of UV diodes internally after the filter. They’re not overly expensive units. The idea being that the air will pass th

You can buy HEPA units that have a strip of UV diodes internally after the filter. They’re not overly expensive units. The idea being that the air will pass through: Charcoal (activated carbon) -> HEPA media -> UV light. There are some arguments that the UV stage might lower air quality by causing particulates to adhere to room surfaces due to electrostatic charge (i.e. particulate counts would drop rapidly due to particles sticking to walls and furniture, but would then drop off as the charge dissipates and return to room air after the filter is off). I’m not sure how relevant this is - as the filter would catch the particles on the next cycle so I guess it would depend on if the unit is running 24/7 or only some of the time. Mine failed under warranty and wasn’t replaced with a UV unit due to concerns about Ozone.