Partial inerting – A possible means of eliminating the brush-discharge-ignition hazard with explosive gases and vapours?

It was found that the brush discharge ignition hazard with IIA gases/vapours (propane) can be eliminated by reducing the oxygen/nitrogen volume ratio in the atmosphere to the order of 15/85. The condition is that the diameter of the earthed electrode ≤ 40 mm. Published information on whether an oxygen/nitrogen ratio of 15/85 is acceptable as regards the oxygen deficiency hazards is contradictory. With IIB gases/vapours (ethylene) the oxygen/nitrogen ratio must be reduced to at least 10/90 to eliminate the brush-discharge-ignition hazard. Lowering the oxygen/nitrogen ratio to this level will undoubtedly present a substantial oxygen deficiency hazard to humans.