NEGATIVE PRESSURE ROOMS
The Uniform United States Building Codes and the ASHRAE Hospital Guidelines are similar. The Building Code table allows the use of recirculated air if a HEPA filter is used.
Below I have tried to detail the recommended items to make a negative pressure room. Your room may be simpler or more complex. Different systems abound. They vary from the simple recirculation of air from a room unit and no supply air from the building HVAC unit to a very complex set of air ducts, balancing or motorized dampers. Call me with details when you have had a chance to review your systems with this information.
If there is a room unit HVAC fan coil unit, and if one calls this room an isolation room, we also make an adapter for the fan coil unit that provides HEPA filters as well as UVGI for double safety of the unit when the air flows back into the room.
If no ante room, exhaust from NQ unit would be the total 250 cfm supply air amount not 175 cfm. The toilet exhaust would then satisfy the negative pressure or the required air around the doorway or 50-75 cfm. This amount makes the room a negative pressure room.
