There is a limit to the pressure differential that should be maintained between a laboratory and adjacent spaces because of the need to enter and leave the laboratory through doorway(s). Typically, safety concerns are satisfied with a negative differential, i.e., air flow towards the laboratory, in the range of 0.01 to 0.02 inches W.G. A small, discernible air flow is noticed through an open doorway with a pressure differential of 0.01 inches W.G. However, a pressure differential of 0.35 inches W.G. requires a force of about 20 pounds to open the door, which is too much in the view of many laboratory operators. Wiseman (2003) recommends using a sliding door instead of a traditional swinging door. When a swinging door is used, "it should open out of a negative room [hazardous isolation] or open into a positive room [protective isolation]." [Wiseman, 2003] [Laboratory Control and Safety Solutions Application Guide, 1994]
