An apparatus (12) includes a primary housing (20) constructed from sheet metal by stamping, a primary inflation fluid source (100), a secondary housing (70) constructed from sheet metal by stamping, and a secondary inflation fluid source (200). The primary inflation fluid source (100) is located in the primary housing (20) and is actuatable to effect a primary flow of inflation fluid out of the primary housing to inflate the inflatable device (14). The secondary housing (70) is disposed within the primary housing (20). The secondary inflation fluid source (200) is located in the secondary housing (70) and is actuatable to affect a secondary flow of inflation fluid to supplement the primary flow of inflation fluid. The secondary housing (70) has a first portion (77) that moves at least partially out of engagement with a second portion (74) of the secondary housing (70) when the secondary inflation fluid source is actuated.