The engine shall be provided with a suitable exhaust system capable of carrying exhaust gases from the engine and dissipating them to the atmosphere as efficiently, quickly and silently as possible. Exhaust pipes shall be black steel pipes of minimum 3 mm thickness and shall be sized so that the back pressure created will not exceed the amount recommended by the generator set manufacturer and the output power of the engine will not be derated. The whole exhaust system shall be adequately supported with spring isolators. A suitable flexible connection shall be made between the section of piping fixed to the engine and the piping fixed to the building structure to allow for expansion/contraction and for vibration isolation. The exhaust pipes outside the generator room, where exposed, shall be lagged with non-combustible thermal insulating materials and have a thickness of not less than 75 mm. The lagging shall be protected by a aluminium sheet cladding of minimum 1 mm thick constructed in sections. In similar construction, the exhaust pipe in the generator room shall also be properly lagged in order to protect against any harmful thermal effects to personnel in carrying out operation and maintenance. Penetration between the exhaust pipe and the exterior wall shall be sealed airtight with non-setting resilient caulking compound. Each section of the cladding shall be removable for replacement of the insulating materials. No flanged joint shall be used. The non-combustible thermal insulating material provided shall be of non water absorption type and capable of maintaining the external cladding temperature not exceeding 40 0C. Asbestos shall not be used for lagging. Suitable temperature detectors shall be provided for each exhaust manifold to monitor the exhaust temperature. High exhaust temperature shall cause an alarm and the generator set stop to operate. The exhaust system shall incorporate an efficient primary silencer of reactive type and secondary silencer of absorption-type capable of reducing the exhaust noises of the engine to an acceptable level as in the specification – Specification for Acoustic Treatment for Generator Room. The silencers shall comply with the specification – Specification for Acoustic Treatment for Generator Room, and shall be supplied together with the generator set by the registered supplier.