Wall Poster A full-color wall poster entitled “How to Use the MSA Model 401 Pressure Demand Air Mask” is available from Mine Safety Appliances Company. The 20 x 26-inch poster offers a handy illustrated reference to routine procedures for donning, checking and removing the apparatus. It also features a color-coded schematic drawing of air flow from the cylinder through the regulator to the facepiece. The schematic pinpoints the relative location of all valves, the pressure gauge and the diaphragm. It is accompanied by an exploded view of the exhalation valve in the facepiece.