Gas appliances connected to electricity have accessible adjacent isolation (in Australia, for example, a plug into a switched outlet that can be reached), and anything that could ignite gas (outlets, switches, light fittings, switchboards, meter boxes, air conditioners) are kept out of hazardous areas around gas cylinders and gas relief vent terminals as the standard's figures define.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.