Do you know what a seatbelt pretentioner is? If so, give yourself a prize. Since I have been training professionally and speaking on the safety system addressed in Federal Motor Vehicle Standard 208, I regularly ask my students this question.  Most people don’t know what it is, or what it’s designed to do.

Many people confuse the pretentioner with the fast-braking belt-locking system. The fast-braking lock is a mechanical device that restricts the slack of the belt in case of a fast stop or brake application. It can be placed at various places within the seatbelt system. It works almost like a pendulum when the brakes are applied aggressively. As the pendulum is forced forward due to the fast stop, it locks into the seatbelt mechanism and restricts the belt from releasing any more slack.

The pretentioner is different, however. The seatbelt pretentioner is a pyrotechnic device that works with the fast braking lock system. The mechanical locking device restricts any more slack, and the pretentioner takes up the slack that is there and pulls the occupant back into the seat. The pretentioner works on the same circuit as the other airbags in the vehicle so that all systems work together.

Some of you may have heard of victims of serious collisions having a burn mark where their seatbelts crossed their torso. That is the pretentioner doing its job of pulling the occupant back toward the seat. You may have a mark for a while, but it can save your life.

When a door glass, vent glass or any tempered part in a vehicle breaks, the glass can go anywhere. If some of the glass chips get into the housing that surrounds the pretentioner, then removal must be done with caution. You should not dig down into the pretentioner housing to retrieve any broken glass.  Tools digging down in the housing could cause damage to the electrical system that triggers the pretentioner.

To clean out the housing:

• Use a vacuum cleaner to suck out broken glass pieces;
• Use compressed air to blow out the debris;
• Manipulate the belt to force out glass chips; and
• Disassemble the housing and clean out the pieces of glass trapped within. The housing is quite simple to remove, and the results will be cleaner with less chance of malfunction.

My advice is not to ignore the seatbelt area when cleaning up a tempered glass break. It can cause a malfunction of the system and possible injury to the vehicle owner or passenger. Just be careful when working in or around the pyrotechnic pretentioner—the cost and time needed to replace it will most definitely eat into your profits on the job.

Bob Beranek is the president of Automotive Glass Consultants Inc.