From: Notes on the apparatus used in determining the respiratory exchange in man: I. an adaptation of the French gas max for use in respiratory work, by Cameron Bailey, J. Biol Chem 1921; 47:277-279.

“The rubber gas mask used in the French army is admirably suited to this work. It is made of thick rubber, covers the whole face, and presents broad surfaces which closely engage the forehead, sides of the face, and jaw. The tissues in these regions are well supported by the bony framework of the face and the mask readily adapts itself to these fixed surfaces. It is held in place by elastic straps passing around the head. In emaciated subjects, leaks may occur above of below the zygoma, in the area the pull of the straps is in the same plane as the surface of the face. In such rare instances the leaks are overcome by placing 6 inch rubber sponges over these areas of the mask and binding them firmly in place with a 3 inch bandage. In this mask, the incoming air is directed upwards towards the windows, the opening of the expiratory tube being opposite the nose and mouth. In this way the space is perfectly ventilated and no discomfort results. Rubber flutter valves are eminently satisfactory for use with these masks. They are conveniently enclosed in flattened glass tubes introduced as near the mask as practicable. A satisfactory arrangement of mask valves for the Tissot method is shown in Fig. 1. The subject reclines in a wheel chair in the rest room, the tubes pass through the wall into the laboratory where the valves are mounted, the tubes then lead directly to the air supply and to the gasometer. A window permits the operator in the laboratory to observe the subject, while at the same time he can follow the respirations by watching the movement of the valve and start and stop the test by turning the 3-way valve on the gasometer.”