A Slow-Motion Video of a Pyrotechnic Seat Belt Pretensioner Activating at 28,000 Frames Per Second

In the latest video by The Slow Mo Guys, hosts Gavin Free and Daniel Gruchy record a pyrotechnic seat belt pretensioner explosively activating in slow-motion footage recorded at 28,000 frames per second. If you’re unaware: A seat belt pretensioner holds a passenger in their seat during a car accident by rapidly tightening the belt. The pretensioner keeps the passenger in an optimal position for airbag operation and also prevents “submarining,” a dangerous condition in which the passengers slips underneath the lap belt in an accident.