42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.
(a) Airflow resistance shall be determined when the respirator is completely assembled with the respiratory-inlet covering and the hose in the maximum length to be considered for approval, coiled in loops 1.5 to 2.1 m. (5 to 7 feet) in diameter.
(b) Airflow resistance shall not exceed 38 mm. (1.5 inches) of water-column height to air drawn at the flow rate of 85 liters (3 cubic feet) per minute.
(c) The exhalation resistance shall not exceed 25 mm. (1 inch) of water-column height at this flow rate.