CFR › Title 42 › Part 84 › §84.15842 CFR §84.158Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗Copy link(a)Dry exhalation valves and valve seats will be subjected to a suction of 25 mm. water-column height while in a normal operating position.(b)Leakage between the valve and valve seat shall not exceed 30 milliliters per minute.