I'm not an HVAC pro . . . far from it. That said, every HVAC tech I've talked to - and I've talked to a lot over the last 9 months in preparation for a crawl space overhaul that we completed in March - has recommended the Aprilaire 5000 whole house air purification system. https://www.aprilaire.com/whole-house-products/air-purifiers/model-5000
I know nothing about HVAC. But the gf is a pro at it and has designed and built a few modules in her career.
I will ask her.
I am an HVAC engineer. I've specified one for an apartment clubhouse. Personally, I would say that if you have allergy issues (ie, more than one member of your family has seasonal allergies to pollen or grasses) or stinky pets, then yeah, it might be worth it. They can reduce odors and smells in a house significantly. If you are doing it because you are worried about bacteria / viruses, then I would say pass. They WILL pull out almost all of the viruses / bacteria in the air, but it isn't exactly a worry-inducing amount to begin with.
We have a cat that occasionally pisses outside the litter box and my youngest I suspect has allergies. We haven’t gotten him tested yet, but he sneezes/snots a lot. Hell maybe he’s allergic to the cat? But I didn’t know if any of these products that are out there would help with either situation.
As I said, they are better for pulling odors out of the air than anything. I would not recommend using this kind of system to alleviate a child's allergy issue to an animal. They are better for pulling pollen out of the air because the air that enters your house through doors / windows has small particles of pollen that can travel farther distances and can be pulled into your HVAC system return air grilles. Depending on the size of the house and how open it is, you probably have about 3 to 7 return grilles scattered throughout the house. With pets, the dander that they are spreading does have an airborne component, but the little bastards also drop it on every surface they touch. The air purifiers wont pick up that dander because it is already sticking to the surfaces. So unless your cat spends 90% of the time sitting in front of a return grille or you go around constantly beating all the surfaces of your couch / floor where the cat has been, you're not going to alleviate the problem enough to get your son to stop dribbling snot (if he is indeed, allergic).
Hard to say. The system I installed / specified was a Trane system that was a multi-tiered system that used HEPA filters, UV light, and an ionizer system. I thought it was major overkill, but I think the owners were worried about smells coming from the clubhouse kitchen (it was a retirement community apartment complex clubhouse, so half of the clubhouse was a full kitchen that was serving meals twice a day). Never heard any complaints in the 2 years it's been running. Unfortunately, I have no clue what the overall cost was.
