§ 84.157 Airflow resistance test; Type C supplied-air respirator, pressure-demand class; minimum requirements.
(a) The static pressure in the facepiece shall not exceed 38 mm. (1.5 inches) of water-column height.
(b) The pressure in the facepiece shall not fall below atmospheric at inhalation airflows less than 115 liters (4 cubic feet) per minute.
(c) The exhalation resistance to a flow of air at a rate of 85 liters (3 cubic feet) per minute shall not exceed the static pressure in the facepiece by more than 51 mm. (2 inches) of water-column height.