Abstract: An initiator assembly (140) comprises a retainer (46), which can be the cover for an inflator housing (10), and an igniter (142). An opening (85) is formed in the retainer (46). The igniter (142) has a longitudinal axis (143) and comprises a pyrotechnic material (152, 156) on the axis. The pyrotechnic material (152, 156) on ignition exerts a force along the axis (143). The assembly further comprises a preformed compressible plastic coupler plug (148) which includes a plug portion (170) received within the retainer opening (85). The coupler plug (148) comprises locking surfaces (184, 188) which engage the igniter (142) and the retainer (46) and hold the igniter in a spaced relationship with respect to the retainer. The plastic coupler plug (148) further comprises an inwardly extending compressible web (174) integral with the locking surfaces (184, 188). The compressible web (174) provides a seal in the space between the igniter (142) and the retainer (46).