Abstract: An airflow system for use with a helmet includes a face piece adapted to enclose the eyes of the wearer to form a first cavity and to enclose the nose and mouth of the wearer to form a second cavity isolated from the first cavity. Filtered air normally flows through an inlet to the first cavity, from which it flows to the second cavity through a conduit and eventually to the ambient region through an exhalation duct leading from the second cavity. The air is supplied under pressure to the first cavity and the exhalation duct provided with check valves at its inlet and outlet to maintain a positive pressure in the first cavity, thereby to prevent the infiltration of noxious gases, over most of the breathing range. A spring-loaded check valve normally admits additional air directly to the second cavity through a second inlet to prevent excessive airflow through the first cavity across the eyes of the wearer.