WHAT ARE NEGATIVE PRESSURE ROOMS?
The goal of a negative pressure room is simple. If someone is exhaling a virus or other contagion into the air, “you create a vacuum—a rather low-[pressure] vacuum,” Streifel says. “You have to suck out more air than you are blowing in.”
That means an airborne infection isolation room is actually just one big vacuum. Generally speaking, it sucks in air through the gap under the door to the hallway. Yes, that means it’s sucking in air from a common space—meaning the air entering the room isn’t designed to be sterile. Then, an exhaust fan—often located in the bathroom—will eject the diseased air in the room to the outside.
These rooms have a few other features to maintain negative pressure. The windows can’t be opened. The doors close automatically. But most of all, these rooms need to spit out 30% to 40% more air than they are taking in at any moment. That’s what creates the pressure, or the one-way flow of air.