If specified in the Bill of Quantities or in the Drawings, air ventilation system shall provide effective generator room cooling and to maintain the ambient temperature rise not higher than 10 0C when the generator set is not in operation. A fan assisted ventilation system capable of a minimum of twenty air changes per hour within the building shall be designed to provide positive ventilation into the generator room. The Electrical Contractor is required to submit calculation worksheet together with all data/characteristics to meet this requirement. Ventilation fan shall be of low speed type not more 1000 rpm, 240 V, 50 Hz and of high quality mild steel casing construction with die-cast aluminium alloy aerofoil impeller blades. Suitable ducting system with air inlet/outlet grills shall be incorporated. All openings through walls and ducting system shall be treated acoustically complying with the specification – Specification for Acoustic Treatment for Generator Room. The Electrical Contractor shall also provide electrical wiring in galvanised steel conduit for the ventilation fan complete with all necessary isolation, protection, control and starting/stopping equipment.