[aroch]

I'm mostly familiar with ER design so I may be off, as far as what "normal" rooms are like. But from my recollection there was a push after 9/11 to move any new isolation rooms to negative pressure and there were subsidies in place to encourage that. There was also a push to redo airhandling for standard rooms to approximate negative pressure but with less stringent scrubbing.

[giarc]

You could be correct, I'm not familiar with post 9/11 IPC planning in the States, however I highly doubt that all isolation rooms in the USA are negative pressure. I assume the post 9/11 push was for all hospitals in urban settings to have at least negative pressure isolation room (very different from an isolation room).