A hybrid inflator including an inflator housing having an outer wall and a pop-out diffuser. The outer wall defines a compressed gas reservoir and contains a combustion chamber separated from the compressed gas reservoir by a rupturable burst diaphragm. An initiator and pyrotechnic gas generant are contained within the combustion chamber of the inflator housing. The initiator is connectable to a remote collision or deceleration sensor through an initiator port defined by the outer wall. Compressed inert gas is contained within the compressed gas reservoir. The pop-out diffuser includes a diffuser plate forming a unitary part of the outer wall and a rupturable seam divides the diffuser plate from the remainder of the outer wall. A diffuser sleeve extends from the diffuser plate into the compressed gas reservoir to a diffuser flange extending radially outwardly from the diffuser sleeve and having an outer diameter that is greater than an outer diameter of the diffuser plate. The diffuser sleeve defines a plurality of gas exhaust ports. Upon initiation of the inflator, the initiator ignites the pyrotechnic gas generant which burst through the rupturable burst diaphragm to heat the compressed inert gas. The heated compressed inert gas pressurizes and causes the rupturable seam of the diffuser plate to rupture and form a portal so that the pop-out diffuser will extends out of the outer wall through the portal. The compressed inert gas can then exit the inflator through the gas exhaust ports of the diffuser sleeve and be dispersed for inflating an inflatable airbag cushion.