Smoke Exhaust systems are designed to extract hot gases from compartments affected by fire. As the fire is restricted to travelling inside the duct, it is often assumed that the suspension rods to these HAVAC systems do not require FRL upgrading or consideration. Although the fire will be restricted inside the duct, AS 1668.1 requires that the ‘System’ works under any circumstance. So in the case that the duct travels through another fire compartment, it must satisfy both the integrity as well as insulation criteria. In line with stair pressurization ducts, any hanging rods must have equal FRL as the ductwork, or alternatively, the hanging rods must be fire engineered.