A diffuser for a supplemental restraint system includes a top wall, a cylindrical side wall and a bottom wall defining a diffuser chamber. The diffuser is used in a supplemental restraint system having an airbag and a combustion chamber for providing a pressurized gas to inflate the airbag. The combustion chamber defines an opening therein for exhausting the pressurized gas. The diffuser is a substantially cylindrical member defining a longitudinal axis. The bottom wall has an opening having a predetermined flow area, that is adjacent to and separated from the combustion chamber opening. The diffuser includes a plurality of elongated slots formed therein by lancing, that are generally parallel to the diffuser axis. The slots are configured, and have a flow area, to rapidly inflate the airbag. The slots are further configured to retain debris generated from the combustion chamber within the diffuser and to prevent the debris from entering the airbag upon inflation. The slots are formed by lancing that forms first and second flashing portions on an interior of the cylindrical side all that remain connected to and intact with the side wall upon formation.