For installations over 1,000 volts, nominal, these locked or monitored rooms, enclosures, or vaults must have a warning sign on the door reading, “ DANGER – HIGH VOLTAGE – KEEP OUT. ”The coordinated ANSI Z535 criteria apply to every temporary or permanent safety sign or tag on a utility system. Safety signs are comprised of a signal word panel and a message panel, in many cases augmented by a safety symbol panel. Most projects follow a combination of IEC protection guidelines, IEEE standards, and local electrical codes that govern layout. (B) The live parts are installed at a height, above ground and any other working surface, that provides protection at the voltage on the live parts corresponding to the protection provided by a 2. 4-meter (8-foot) height at 50 volts. (2) Prevent access by unqualified persons. That's why the substation needs a control house.