When, in the course of assembly, dismantling or lifting work on frames and structures, workers are called upon to intervene where they are exposed to the risk of falling into a void, the employer shall take one of the following measures:
1° Installation of fixed work floors, fitted with guardrails placed at a height of 90 centimetres and skirting boards at least 15 centimetres high;
2° Implementation, under the conditions provided for in Article R. 4534-98, of mobile work platforms, or any other similar devices, suspended from lifting equipment.