An apparatus (10) for inflating an inflatable vehicle occupant protection device (12) comprises a container (14) defining a chamber (16). The container (16) has an opening (24) through which fluid can flow from the chamber (16). A quantity of inflation fluid (20) is in the chamber (16). A burst disk (30) closes the opening. The burst disk (30) has first and second opposite major side surfaces (34, 36). The burst disk (30) has a first score line (40, 42) on the first major side surface (36) and a second score line (46, 48) on the second major side surface (34). The burst disk (30) is rupturable at the first and second score lines (40, 42, 46, 48) to permit inflation fluid (20) to flow out of the chamber (16) through the opening (24) in the container (14).