{"data":{"id":"us/42-cfr-84.91","jurisdiction":"us","citation":"42 CFR 84.91","heading":"Breathing resistance test; exhalation.","body":"(a) Resistance to exhalation airflow will be measured in the facepiece or mouthpiece of open-circuit apparatus with air flowing at a continuous rate of 85 liters per minute.\n(b) The exhalation resistance of demand apparatus shall not exceed 25 mm. (1 inch) water-column height.\n(c) The exhalation resistance of pressure-demand apparatus shall not exceed the static pressure in the facepiece by more than 51 mm. (2 inches) water-column height.\n(d) The static pressure (at zero flow) in the facepiece shall not exceed 38 mm. (1.5 inches) water-column height.\n(e) Resistance to exhalation airflow will be measured in the facepiece or mouthpiece of closed-circuit apparatus with a breathing machine as described in § 84.88, and the exhalation resistance shall not exceed 51 mm. (2 inches) water-column height.","path":["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","PART 84—APPROVAL OF RESPIRATORY PROTECTIVE DEVICES","Subpart H—Self-Contained Breathing Apparatus"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-42.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:11Z","sha256":"dfdced630580f315964ea9a46a335bab2cbbf1b9ddbc92e412f947817003493d","source_id":"us-cfr","stale":true,"prev":"us/42-cfr-84.90","next":"us/42-cfr-84.92"},"notice":"GroundRules: Original legal text. Not legal advice."}