An igniter's housing is bored continuously there through to define, in succession, several bore regions. A firing pin, slidingly fit in the first bore region, terminates in a tip that protrudes into a primer-filled second bore region when the firing pin is fully seated in the first bore region. An air-filled third bore region follows the second bore region. An open-ended cup is fitted substantially in and sealed to the fourth bore region with the cup's closed end being structurally weakened at a portion thereof. A bored out slug of pyrotechnic material is fitted in the cup.