RE: I invested in an air purifier, surprising result, here is what I learned about air quality.

There are also UV Sterilization lamps available to treat rooms of germs, bacteria and viruses. If you google it, you would find many on Amazon. However, there are safety precautions: you should not be in the room while it is being treated, nor any pets or plants. While the lamp is running, exposure is a health hazard. You start them usually with a remote control. These are used also to kill moulds. This in addition to air purifiers. But I also seen some air purifiers advertised that have a UV light inside the unit in the filter stage to kill bacteria. From what I've seen, the replacement filters cost at least half as much as the unit.