See the little green ball in the picture above? That gives doctors and nurses a quick view of which direction the air pressure is flowing in isolation rooms. Patients who have their immune systems suppressed, such as those receiving stem cell or bone marrow transplants, need to be in a room with positive air pressure, meaning air flows out of the room to keep out harmful bacteria. The isolation rooms have sliding glass doors, and when they are closed the ball should pop out to indicate positive air pressure. Patients who are highly contagious need to be in rooms with negative air flow to keep the germs in. In that case when the door is closed, the ball should roll out of sight. It’s a simple solution, but a quick and easy way to tell if the door isn’t closed completely or the air pressure system is malfunctioning. Despite all the new technology in the Center for Care and Discovery, sometimes a low-tech solution is best.