42 CFR 84.149 - Type C supplied-air respirator, demand and pressure demand class; minimum requirements.
(a) Respirators tested under this section shall be approved only when used to supply respirable air at the pressures and quantities required.
(b) The manufacturer shall specify the range of air pressure at the point of attachment of the air-supply hose to the air-supply system, and the range of hose length for the respirator. For example, he might specify that the respirator be used with compressed air at pressures ranging from 280-550 kN/m. 2 (40 to 80 pounds per square inch) with from 6 to 76 m. (15 to 250 feet) of air-supply hose.
(c) The specified air pressure at the point of attachment of the hose to the air-supply system shall not exceed 863 kN/m. 2 (125 pounds per square inch gage).
(1) Where the pressure in the air-supply system exceeds 863 kN/m. 2 (125 pounds per square inch gage), the respirator shall be equipped with a pressure-release mechanism that will prevent the pressure at the point of attachment of the hose to the air-supply system from exceeding 863 kN/m. 2 (125 pounds per square inch gage).
(2) The pressure-release mechanism shall be set to operate at a pressure not more than 20 percent above the manufacturer's highest specified pressure. For example, if the highest specified pressure is 863 kN/m. 2 (125 pounds per square inch), the pressure-release mechanism would be set to operate at a maximum of 1,035 kN/m. 2 (150 pounds per square inch).