The ductwork requiring upgrading must have dimensions not exceeding those Tested by LAF and approved by the CSIRO.
Stair pressurisation systems require full integrity of the system and therefore the hanging rod must have the same FRL as the ductwork. With Fire Engineered systems, and in certain particular circumstances (ie rod loads are below 50% of the maximum allowable load) Fire rating of the rods may be omitted. Refer to LAF for further details.
Smoke Exhaust systems are designed to extract hot gases from compartments affected by Fire. As the Fire is restricted to travelling inside the duct, some wrongly deduce that the suspension rods do not require FRL upgrading. The Fire may be restricted inside the duct but AS 1668.1 requires that the ‘System’ work under any circumstance. If the duct travels through a different compartment (which may be engulfed by Fire) the Designer must ensure that the duct will remain in place for the required period of time and the suspension rods must therefore be upgraded.
For Kitchen Exhaust ductwork, AS 1668.1 requires the sheet metal to be of 1.2 mm gauge. With ‘Vermiduct’ 1.0 mm sheet metal is all that is required for ductwork up to 4.8 m wide x 3 m deep. In some special cases ducting not exceeding 1200 mm x 1200 mm may be constructed from .8 mm sheet metal. Please note however that in some cases (ie high pressure ducts etc) greater metal thickness may be warranted! Refer to LAF for further details.
Fan enclosures should be addressed with meticulous detailing. AS 1668 and other recognised Standards require the ‘full system’, not just the sheet metal ductwork, to be Fire Isolated. This means that the fan, as well as the motor should be Fire Isolated. LAF have systems which have been Tested and approved by the CSIRO to provide large (2.4 m x 5 m x 3.6 m high) enclosures with up to 240/240/240 FRL.
Services (Actuators, motor drives, smoke detectors, etc) to be attached to Fire Rated Ductwork can remain in full view and at the same time be Fire Isolated. LAF’s tested systems include for the provisions of inspection enclosures fitted with proprietary intumescing grills to achieve a 2 Hr FRL. The Grills allow the relevant item (smoke detector etc) to remain in view through the grill at all times.