Among many equipment for passenger safety,the air bag system is the most fundamental and effective device foran automobile.The inflator housing is a main part of the curtain-type air bag system,which supplies high-pres-sure gases in pumping up the air bag-curtain which is increasingly being adapted in deluxe cars for protectingpassengers from the danger of side clash.However,flow information on the inflator housing is very limited.Inthis study,we measure the instantaneous velocity fields of a high-speed compressible flow issuing from the exitnozzle of an inflator housing using a dynamic PIV system.From the velocity field data measured at a highframe-rate,we evaluate the variation of the mass flow rate with time.The dynamic PIV system consists of ahigh-repetition Nd:YLF laser,a high-speed CMOS camera,and a delay generator.The flow images are taken at4000 fps with synchronization of the trigger signal for inflator ignition.From the instantaneous velocity field dataof flow ejecting from the airbag inflator housing at the initial stage,we can see a flow pattern of broken shockwave front and its downward propagation.The flow ejecting from the inflator housing is found to have very highvelocity fluctuations,with the maximum velocity at about 700 m/s.The time duration of the high-speed flow isvery short,and there is no perceptible flow after 100 ms. Among many equipment for passenger safety, the air bag system is the most fundamental and effective device foran automobile. Inflator housing is a main part of the curtain-type air bag system, which supplies high-pres-sure gases in pumping up the air bag-curtain which is increasingly being adapted in deluxe cars for protectingpassengers from the danger of side clash. However, flow information on the inflator housing is very limited. Since study, we measure the instantaneous velocity fields of a high-speed compressible flow issuing from the exitnozzle of an inflator housing using a dynamic PIV system. From the velocity field data measured at a highframe-rate, we evaluate the variation of the mass flow rate with time. dynamic PIV system consists of ahigh-repetition Nd: YLF laser, a high-speed CMOS camera, and a delay generator. The flow images are taken at 4000 fps with synchronization of the trigger signal for inflator ignition. Flash the instantaneous velocity field data of flow ejecting from t he airbag inflator housing at the initial stage, we can see a flow pattern of broken shockwave front and its downward propagation. the flow ejecting from the inflator housing is found to have very highvelocity fluctuations, with the maximum velocity at about 700 m / s. The time duration of the high-speed flow is very short, and there is no perceptible flow after 100 ms.