In existing commercial aircraft the air conditioning system delivers air to the cabin for temperature control and cabin pressurization. The conditioned air introduced into the passenger cabin flows down to the utility tunnels under the floor through the sidewall vents and to an outflow valve or valves located on the fuselage of the aircraft and eventually to the ambient pressure. The function of the vent system is to provide cabin air distribution flow control and also to provide decompression protection. In the event of a fuselage decompression the pressure differential between the upper and lower compartments must not exceed the structural limits of the cabin floor. The cabin vent system is designed to limit this pressure differential by increasing the flow area between the upper and lower compartments in the event of a rapid decompression. The differential pressure loads on the floors were analyzed using a rapid decompression computer code.
Lab testing was performed to verify the differential pressure at which the mylar panel ruptures. This testing used a vacuum chamber test setup. The sidewall vent system was exposed to ambient air pressure on one side and quickly exposed to the vacuum system pressure on the other side. These test results were used in the rapid decompression analysis. There are multiple sidewall vents along the length of an aircraft cabin. Therefore aircraft testing was utilized to verify airflow distribution in the aircraft.