[Code of Federal Regulations] [Title 42, Volume 1] [Revised as of October 1, 2004] From the U.S. Government Printing Office via GPO Access [CITE: 42CFR84.77] [Page 520-521] TITLE 42--PUBLIC HEALTH CHAPTER I--PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES PART 84_APPROVAL OF RESPIRATORY PROTECTIVE DEVICES--Table of Contents Subpart H_Self-Contained Breathing Apparatus Sec. 84.77 Inhalation and exhalation valves; minimum requirements. (a) Inhalation and exhalation valves shall be provided where necessary and protected against damage and distortion. [[Page 521]] (b) Exhalation valves shall be-- (1) Protected against external influence; and (2) Designed and constructed to prevent inward leakage of contaminated air.