However, Zero has designed and tested other systems against air leakage to demonstrate the effectiveness of these products and materials at higher pressures. They have been tested for air infiltration (positive pressure) where high pressure pushes the door against the seal, and also for the more onerous air exfiltration (negative pressure) where high pressure pushes the door away from the seal. By specifying a complete "Air Control System" you are assured that the components installed for head, jamb and sill will perform properly together.
The table opposite shows tests conducted under positive and negative pressure at 25 Pa (14 mph), 76 Pa (25 mph), 100 Pa (28 mph), 150 Pa (35 mph), 306 Pa (50 mph), 688 Pa (75 mph), and 1223 Pa (100 mph).
Positive pressure (air infiltration) - where high pressure pushes the door against the seals. For example, external outward opening doors with panic exit devices.
Negative pressure (air exfiltration) - where high pressure pushes the door away from the seals. For example, computer rooms, halon systems, hotel bedroom doors etc. Negative pressure tests are the more onerous.
The higher the air pressure differential, the better the quality of the gasketing is needed. Adjustable gasketing facilitates installation and allows adjustment when needed for consistent performance over time.
Properties in Miami-Dade County, Florida are subjected to seasonal hurricane force winds and Zero offers a tried and tested set of seals for such situations. This is known as the "Dade County set". To maximise protection, doors should be designed to open out which means that strong winds will force the door against the seals. The Dade County Set has been tested under positive pressure to a wind velocity of 135 mph and protects against wind-driven water infiltration.