CFR > Title 42 - Public Health > CHAPTER I—PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES > SUBCHAPTER G—OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES (parts 80 to 87) > PART 84—APPROVAL OF RESPIRATORY PROTECTIVE DEVICES > SUBPART H—Self-Contained Breathing Apparatus (§84.70 to §84.104) > 84.90—Breathing resistance test; inhalation.

84.90—Breathing resistance test; inhalation.

(a) Resistance to inhalation airflow will be measured in the facepiece or mouthpiece while the apparatus is operated by a breathing machine as described in § 84.88.
(b) The inhalation resistance of open-circuit apparatus shall not exceed 32 mm. (1.25 inch) water-column height (at a flow rate of 120 liters per minute).
(c) The inhalation resistance of closed-circuit apparatus shall not exceed the difference between exhalation resistance ( § 84.91(e)) and 10 cm. (4 inches) water-column height.