On surgical floors Operating Rooms(ORs) have positive pressure checks daily to ensure air handlers are working effectively. Why is positive pressure more desirable for surgery vs. negative pressure? Can either be compared to the exhaust fan in my bathroom on a smaller scale? Thanks!
In: Engineering
I design hospital renovations for a living. Air, and everything that’s in the air, moves from areas of high pressure to low pressures. Certain parts of the hospital need germs to move towards them, or away from, depending on the function. The operating room needs germs to move away from the operating table, so air supplies are positioned directly above the table and force the clean air to hit the table/patient and move away from the table and then return vents are positioned near the floor at the edge of the theater. Positive air pressures are also used in areas where immuno-compromised patients are, such as infusion therapy areas. Negative air pressures are used where we want to keep germs from spreading, such as infectious disease patient rooms. Because of COVID-19, the hospitals I work with are converting normal ICU rooms into infectious disease rooms by adding exhaust systems to those rooms that dump the air outside. Construction sites in the hospital are also negative pressure areas, they use exhaust fans to force air out of the construction area and dump it outside, forcing clean air into the construction zone and then takes the dust out of the building.
So yes, they are very similar to the exhaust fan in your bathroom, in fact the exhaust for your bathroom is often on the ceiling because the warm humid air rises so the fan creates air movement from the floor to the ceiling, which is the natural movement of the warm air. The difference is that your house probably doesn’t have controlled ‘makeup air’. Basically, if you are pulling air out of an area, then air will find its way into the area to balance out. For a house, the air is pulled out by the exhaust fan, and because there usually isn’t mechanical equipment to pull air from the outside, clean/condition it, and put it inside the home in a controlled manner, outside air seeps through the cracks in your house. Hospitals have dedicated makeup air units that will draw air through filters and condition the air before putting inside the hospital. This allows the hospital to control the air from the moment it enters until the time it is exhausted.
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