Airbag seam testing

Airbag seam testing

Seat airbags are designed to deploy upon side impact only. In an accident, in-car sensors detect the impact and sends a signal via the SRS control module to the seat airbag.

Airbags are usually internally tethered for guidance and reinforced to prevent them from ripping under the extreme pressures involved in their deployment. At the heart of every airbag is a hybrid gas generator. This is a canister filled with a high-pressure gas and a flammable substance.

When an electrical signal reaches the canister, it fires the charge, which, in turn, releases the high-pressure gas. Rapid release of the gas inflates the airbag. When the airbag is deployed, it breaks out of its holder and bursts through the seat seam. This allows the airbag to inflate fully. All this happens within a fraction of a second.

If a seat seam has been altered outside of the manufacturer’s specifications, the airbag could deploy too early, or too late, or, possibly in the wrong position, and it won’t be effective. This means that any work done on seat upholstery must be done by someone who not only understands how airbags work, but also has an in-depth knowledge of the car seat upholstery trade. At RVE, we have in-house experts that understand the procedures and testing required to validate seat seams that release when an airbag deploys. 


Through extensive testing, RVE have verified that every vehicle model needs to have a different thread combination to ensure compatibility.

All our airbag seams are sewn using data from comparative tests that verify the tensile strength of the original factory seams. This information is used to select the correct thread combination. The data is recorded on a tag that is sewn into the airbag seam. Each seam has a unique serial number that can be traced, if necessary, to reveal all the information about the seam.


Comparative testing

As the major New Zealand car upholstery market leader, Retro Vehicle Enhancement has built up an extensive collection of most models’ static test results, which allows us to replace airbag seams with the assurancethat the seams will deploy as intended.

Every model we have worked on since 2000 has had its original seat airbag seams tested, and a comparable test has been done on the new seam.

We also film the airbag deployment using an ultra-high speed ballistics cameras to confirm our comparative test results. The cameras allow us to show the airbag deploying within the time frame stipulated for factory-tested seats. Contact us for more information.


The criteria for the certification of airbag seams include:

  • Original factory covers are tested and a comparison made between the thread combinations of the original and the new seams.
  • The new seams have been stitched according to tested samples.
  • The seat covers have been fitted by a trained installer, using the same method as the original fitment.