Smoke leakage (S): Failure of this criterion shall have happened If your stream fee in duct A in the course of the examination exceeds ten m³ / (m² h), relevant to 20 °C and 1013 mbar, associated with the internal area area of your duct Within the furnace. Based on https://jeffreylbper.madmouseblog.com/17506283/how-fire-rated-ductworth-can-save-you-time-stress-and-money