After years of being a fly on the wall I signed up just to say: most of those things are closer to Radithor than snake oil.
There are only a few companies that sell those things at that price point (installed, $600-$800 for the unit), and they’re all so egregiously fraudulent that I strongly considered doing the leg work for a class action lawsuit.
I got the same pitch a few years ago, but as their bad luck would have it I actually worked on a UV-C LED based germicidal system for years with the same goal in mind, albeit as a hobbyist. My focus was on the LED based variants, which dominates new residential products, so I can’t speak to other systems. That said, regardless of the technology a $1,500 UV-C germicidal HVAC system is a $1,500 MRI machine - no it isn’t.
I was extremely interested in how they managed to accomplish what I had deemed unreasonable with current technology, while also being about 1/4 the cost and 1/15th the power requirements. The latter magic claim is their biggest tell, since the power requirements are slapped on the box and the power supply itself. In this case it was ~17 watts. I’d estimated ~300w for a barely reasonable reduction of common pathogens, and that was based on trying to out-clever systems that used 700w+.
Long story short, I disassembled one of them and they’re regular blue-violet LEDs @ ~405nm, a ceramic fragrance diffuser (popular’ish air freshener in the 90’s) that they marketed as some kind of alien tech UV enhancer, and a high voltage ionizer buried deep in the housing. The last item was going to be my cause for action since they proudly claim zero ozone generation while including a device that is solely intended to produce it. Hilariously I actually had a box of the same ionizers and I think I paid $20 for two scoops of them. I believe they include it so they can technically say the device does indeed have some level of potentially measurable germicidal properties, whereas their purple LEDs would have zero. They never claimed the lights were what did it!
They try bank on a technicality and consumer confusion regarding the LEDs by being very careful to say “UV” on the box, not “UV-C”, and due to inefficiencies of not being a laser the spectral wings of ~405nm purple lights would accidentally qualify as emitting UV. I also think there’s probably a legal loophole that allows the minuscule amount of ozone being generated by the literal ozone generator to qualify as “zero” due to dilution, while still being “germicidal” (if they brush up against the electrodes), so they may be skirting the law there as well. I don’t think the totality of their attempt at legal shenanigans would hold up, but I can’t find any other rational explanation for their very specific design and marketing decisions.
That’s as far as I got with it, since I only had a couple hours to inspect the device, but that was more than enough to make up my mind. Final thought: even if they used enchanted technology that fell from space you may only need to consider the 6-8” wide device being installed directly in the ~18” airflow, and restricting it accordingly, to decide if you’d be happier with an external HEPA filter in a couple rooms instead.