The difference is the speed of gas production. A bomb has an uncontrolled rate, and so is lethal by intent and design. The inflator in an airbag should produce

The difference is the speed of gas production. A bomb has an uncontrolled rate, and so is lethal by intent and design. The inflator in an airbag should produce gas rapidly, but in a controlled manner - more like a rocket engine. The design of the Takata airbags meant that the tablets of fuel would break down into a powder over time, vastly increasing the surface area that was available to burn and thus gas production became uncontrolled.