“The remaining 50% then goes thru hospital grade filters.”
As long as they’re maintained, or even installed. Perhaps you can point us to the FAR requiring filtering for recirculating air?
“Perhaps you can point us to the FAR requiring filtering for recirculating air?”
I’ve already described how airliners are designed. My daughter works maintenance on airliners. If you want to read about aviation regs, you’ll have to do it yourself.