Abstract: A mask-hood assembly for supplying persons, such as aircraft passengers, with clean air or oxygen during emergency situations such as a cabin depressurization, a fire emergency and when the passenger attempts to escape through a smoke-filled environment. The mask is applied and held against the user's face so that it overlies his nose and mouth and communicates with an emergency oxygen supply system via valving disposed in a two-part housing. During escape attempts the passenger separates the two housing parts, one remaining attached to the emergency oxygen supply system and the other one remaining attached to the mask. Upon separation of the two parts, an activated charcoal filter disposed in the housing part attached to the mask is automatically positioned so that the passenger only inhales air from which particulate contaminants, smoke and/or toxic gases have been removed by the filter. A tightly folded hood is wrapped about the exterior of the mask.