What is the minimum clearance that must be maintained on a non-working/access deck?

The correct choice reflects the standard practice regarding minimum clearance on a non-working or access deck. Maintaining a clearance of 450 mm is essential for ensuring safe access and movement on scaffolding structures. This distance helps prevent accidents and allows personnel to maneuver comfortably without obstructions.

In terms of safety regulations, having this specified minimum clearance also ensures that materials and tools can be handled efficiently without risking tripping or other hazards associated with overcrowded or obstructed walking surfaces.

The other measurements, while they could reflect different context-specific requirements, do not align with the standard clearance needed for non-working decks as outlined in scaffolding safety guidelines. Therefore, understanding the context of safety protocols, particularly in construction and maintenance settings, reinforces the importance of adhering to the specified clearance standards.