Squib: From Firecracker to Airbag Igniter

To most people, a squib is a small firecracker or a short, witty remark. The word has roots in 17th-century theater, where it meant a brief satirical piece. By the 18th century it had come to mean a tiny firework, something that fizzles out quickly or produces an underwhelming bang. The sense of anticlimax still clings to the word.

In automotive engineering, a squib is the opposite of underwhelming. It is a small pyrotechnic heating element, typically a nichrome wire embedded in a pressure-sealed capsule, designed to ignite with extreme reliability. When an airbag control module detects a collision through accelerometer sensors, it sends an electrical pulse to the squib. The squib heats to over 1,000 degrees Fahrenheit in milliseconds, igniting sodium azide pellets packed nearby. The resulting chemical reaction produces nitrogen gas at high pressure, inflating the airbag in roughly 30 to 50 milliseconds, faster than a blink.

The squib must perform perfectly the first time, every time, for decades of storage. It has no moving parts and no mechanical reliability concerns. Engineers spec squibs to fire within a narrow electrical window and must isolate them from electromagnetic interference, moisture, and thermal shock. A modern car may have four to ten squibs depending on the number of airbags; larger vehicles can have many more.

The word's migration from frivolous novelty to critical safety component reflects the broader history of pyrotechnics in engineering. Military and aerospace industries borrowed controlled explosives from fireworks makers for similar triggering applications long before automobiles. The squib in an airbag system inherits that tradition: it is a pyrotechnic device stripped of spectacle and refined into precision. The small, contained charge that once meant a dud joke now means the difference between a bruise and a fatality.