On (b) above, it should be mandatory on conveyor walkways or similar parts of the plant where material drops on a consistent basis and where people need to walk under particulary where it is defined as a local thoroughfare locally.This Standard sets out requirements for the design, selection, construction and installation of fixed platforms, walkways, stairways and ladders that are intended to provide safe access to places used by operating, inspection, maintenance and servicing personnel.This Standard also applies to the following:(a) Movable platforms that are permanently configured but that may be site adjustable or site assembled/modified.(b) Permanently installed roof access, where such access is for the purpose of installing, operating, inspecting, maintaining or servicing equipment that is located on, or is accessible from, the roof.(c) Permanently installed access for inspection and maintenance of the roof itself.NOTES: 1 In the absence of a directly applicable Standard, this Standard may be used for guidance in providing access to some parts of stationery and mobile machinery, light and telecommunication towers, wind turbine towers and water and sewerage facilities. On (a) above, it is mandatory and common practice adapt this.

The mandatory 'shall' compels the engineer to adapt this mesh or design an equivalent on 'all' platforms situated over 'trafficable areas.' Metal Steel Scaffold Planks Suspended Aluminum Perforated Metal. This plank will pass the apperture requirement of Clause 4.5. Perforated scaffold planks like these(link below) are installed on both (a) and (b) above as needed - not a permanent fixture everywhere in a gas refinery or mining facility.

(b) a person walking inside a mining facilty where he is inducted and made aware of how his behaviour can impact on his safety and others' safety (a) a person walking to work in the central business district (CBD) where construction is in progress and

There is a huge disparity on risks to dropped objects between AS 1657 covers both commercial and industrial industries.

Australian standard as 1657