Forager, have you ever heard of in-duct ultraviolet light air cleaners? The UV light kills a lot of the bacteria/viruses in the air. Coincidentally, hospitals usually have this installed as part of their HVAC systems, but you can get it on your home, too. I'd never heard of this until recently... you probably know all about it, with DS's lung issues, but I thought I'd mention it *just in case*.
I hope he's doing better VERY soon!
You make your choices, and you live with them. In the end, you are those choices.
"Strength is the mental and physical fortitude to endure, resilience to bounce back, and force to create change, allowing you to thrive in any circumstance and through any adversity." TrPAssassin