Smoke leakage (S): Failure of the criterion shall have happened if the flow amount in duct A in the course of the test exceeds ten m³ / (m² h), connected to twenty °C and 1013 mbar, connected with the internal surface place in the duct inside the furnace. According to https://dantetiwwo.life3dblog.com/35562844/fire-rated-ductworth-an-overview