After a vehicle has been in an accident, the seat belt retractors and/or buckle Alongside the seat belt retractor mechanism, some vehicles come equipped with a deployable buckle pre-tensioner.
This is commonly referred to as the buckle receptacle latch (the unit with the red clickable button on the seat). Some buckle latches are equipped with a pre-tensioner.
To know if your vehicle comes equipped with one, you can scan for codes, or do a visual examination. A buckle pre-tensioner unit will have a long tube attached at the bottom.