For Kitchen Exhaust ductwork, AS 1668.1 requires the sheet metal to be of 1.2 mm gauge. However, with the Vermiduct system, 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 0.8 mm sheet metal.