3.3 Dismounting at HeightAs much of the existing environment control system is installed at height, tested chain block, scissor platform or scaffolding working platform may be used for dismantling works at high level. The area for ductwork demolishing shall be fenced off for protection if necessary. Depending on the size of ductwork, Fans or associated accessories, the dismantled parts shall be hoisted down manually or by mechanical hoisting apparatus. The SWL of the mechanical hoisting apparatus shall be specified and the rigging hardware shall be secured bolted during hoisting.Before lifting, method of lifting shall be selected according to:- Weight of the loads- Height of lists and distance- Number and frequency of lifts- Limitation due to the surrounding environment- Other factors like time and dynamic loadsFor heavy items, mechanical hoisting apparatus shall be chosen for lifting operations,a) Before the operation, region of work shall be fenced and non-approved persons shall be refused to enter the fenced region. Routine check shall be conducted to ensure reliability.b) Anchor bolt / bracket shall be used for mounting chain block in order to lift the dismantled parts to ground. The lifting set up should be examined by RPE in accordance with requirement of the Factories and Industrial Undertakings (LA&LG) Regulations.c) After the heavy dismantled load is grounded, it shall be transported to the dedicated location for temporary storage using crane.