Airbag and SRS — pyrotechnic safety systems

SRS stands for Supplemental Restraint System – the supplementary restraint system that together with the safety belt protects occupants in a collision. The system includes airbags, belt tensioners, sensors, and a control unit. For a mechanic, it is important to understand two things: how it protects, and why it requires great caution to work near it.

§How SRS works

In a sufficiently powerful collision, collision sensors register the rapid deceleration and the control unit decides in fractions of a second which systems should be triggered. The seatbelt tightens the belt so the passenger is held in place and the airbag fills with gas and unfolds as a cushion. The airbag should be empty again before the head hits it — it works in a very short time window and is designed to supplement the seatbelt not replace it.

§Why it is pyrotechnic and dangerous

Both airbags and seat belt pretensioners are activated by a pyrotechnic charge — a small explosive charge that develops gas very rapidly. An airbag that deploys by mistake during work can hit you with great force. That's why you treat SRS components for what they are: small, embedded explosive charges that must be handled with respect and according to the manufacturer's instructions.

§Rules for work around SRS

• 01Look up the manufacturer's procedure before removing steering wheel, dashboard or seats with airbags.
• 02Make the system de-energized and wait the specified discharge time before disconnecting the SRS connector.
• 03Carry or place a removed airbag with the cover side up and away from the body.
• 04Never expose components to impacts heat or open flame.
• 05Never use a universal tester on SRS circuits — only the prescribed diagnostic equipment.
• 06Replace deployed or damaged components; a deployed airbag or tensioner cannot be reused.

§After a pause you read your own text as a stranger — that is where you catch errors that spellcheck does not see.

When a vehicle has been in a collision checking the entire restraint system is part of the repair. Deployed airbags and seatbelt tighteners must be replaced sensors and fasteners checked and fault codes in the SRS control unit read and corrected. A repair where the body is straightened but SRS doesn't work gives the customer false security — the vehicle looks whole but doesn't protect as it should.

§Storage and disposal

Unexpired pyrotechnic components are to be regarded as dangerous goods. They must be stored safely and disposed of according to current rules — not thrown in regular waste. Follow workshop procedures and manufacturer's instructions so an apparently harmless piece of scrap does not become an accident later in the chain.