256.12 Atmosphere above piston-waterless holders.

At least once each week a test shall be made of the quality of the atmosphere above the piston. Smoking and use of devices of any kind that might ignite an explosive mixture shall not be permitted in the piston chamber. All electric lights in space above piston shall be of the vapor-proof type. Electric motors, electric wiring and devices for all uses shall be in accordance with the Fire Underwriters requirements.#