An air bag inflator (10) includes a housing (40) defining a combustion chamber (61) for providing inflation fluid for inflating an air bag. The housing (40) includes radially spaced side walls (50, 60) defining a filter chamber (140) disposed adjacent to the combustion chamber (61) for receiving inflation fluid from the combustion chamber. A filter assembly (150) is located in the filter chamber (140) for filtering inflation fluid flowing through the filter chamber. The filter assembly (150) includes a plurality of nested cylinders including outer and inner cylinders (160, 170). Each one of the outer and inner cylinders (160, 170) includes a plurality of tabs (180, 200) which engage an adjacent side wall (50, 60) of the housing (40) to maintain-the cylinder in position in the filter chamber (140). Each tab (180, 200) comprises an area of the material of the cylinder (160, 170) projecting out of the cylinder and defining a fluid flow opening (182, 220) in the cylinder. The fluid flow openings (182, 220) define a tortuous path for inflation fluid to flow through the filter chamber (140).