What is the logic of building covered in plastic? This reminds me of a south park video.
None. Can still be contaminated.
The room is covered in plastic - that makes it airtight (as opposed to dry walls/ceilings) so that you can create the negative pressure to make the air flow directional.
if you’ve got a gaming PC the case fans serve the same purpose, channeling the air flow in one direction so it doesn’t hang around.
Now, I can see that that would stop contaminated air from hanging around - but all the studies have said it’s not airborne and the most recent studies think that it only travels in droplets (from sneezing, coughing or talking)) so this whole air pressure system is... worthless and masks should do it.