StacksVerified U.S. regulatory reference

42 CFR §84.156

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
  1. (a)Inhalation resistance shall not exceed 50 millimeters (2 inches) of water at an air flow of 115 liters (4 cubic feet) per minute.
  2. (b)The exhalation resistance to a flow of air at a rate of 85 liters (3 cubic feet) per minute shall not exceed 25 millimeters (1 inch) of water.