The roof ventilators shall be of the Gamma Supply Ultra Series  supply air type as designed and manufactured by Fantech Pty Ltd.
Impellers shall be made from high performance injection moulded  composite material. They shall be mixed-flow design and driven  by speed-controllable external rotor motors with integral thermal  overload protection.  
The cowls shall be manufactured from UV-stabilised plastic. Steel  components to be corrosion protected.  
All performance data shall be for a complete assembled unit  based on ISO5801 for air flow and ISO 13347-3 for noise