a) The machinery shall be made of non-flammable material. b) The machinery shall be arranged so as to prevent the formation of dangerous static electricity. c) Explosion relief devices shall be designed so that they do not entail a risk when they open. d) If necessary, the machinery shall be provided with automatic fire extinguishing equipment. A warning signal shall be given before the use of fire extinguishing systems with extinguishing agents that can entail a risk of poisoning.