An airbag safety system for an automotive vehicle includes a housing having disposed therein a gas generator and a retainer which has a lower mounting flat surface for attaching an inflatable airbag tightly to the housing. The housing includes upper and lower members, the upper member being attached to the lower member and having a gas passage allowing gas to flow from the gas generator into the airbag, the lower member having an opening oriented towards the airbag. The upper member further includes an upper mounting flat surface which is formed on a peripheral portion of the gas passage and is contoured to the lower mounting flat surface of the retainer. With this arrangement, the entire circumferential edge portion of the airbag is interposed between the upper mounting flat surface of the upper member and the lower mounting flat surface of the retainer without any clearance for establishing an air-tight seal between the airbag and the housing.