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Subchapter 1. Unfired Pressure Vessel Safety Orders
Article 7. Compressed and Liquefied Natural Gas System

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§542. Warning Signs.

(a) All tanks and cylinders in excess of 60 gallons capacity, except transportation tanks and fuel tanks on motor vehicles, shall have the word "FLAMMABLE" painted or otherwise suitably applied on each side that is readily visible. The letters of this sign shall be standard type and shall have a height of at least 1/12 of the diameter of the tank, but need not be in excess of 1 1/2 inches for tanks of 575 gallons capacity or less, or 4 inches for tanks exceeding 575 gallons capacity.

Transportation tanks shall have warning signs as required by the Department of Highway Patrol.

(b) Warning signs with the words "NO SMOKING OR OPEN FLAMES PERMITTED WITHIN ____FEET" shall be painted or otherwise suitably applied in letters at least 1 1/2 inches high, in sharply contrasting colors on each stationary tank or on a sign posted adjacent to the tank. This sign shall also be posted adjacent to all loading and unloading terminals and vaporizers located more than 50 feet from the tank.

NOTE: The distance shall be that shown in the following table:
Volumetric Capacity of Tanks and Cylinders in U.S. Gallons Minimum Distance From Open Flame
60 to 575 U.S. gallons inclusive 10 feet
576 to 2,000 U.S. gallons inclusive 25 feet
Over 2,000 U.S. gallons 50 feet

(c) When 2 or more tanks are installed in battery, the requirements of Order 542(a) and (b) will be considered as being complied with when the required warning signs are prominently displayed on all exposed sides of tanks.

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