Propane Tank Risk Management and Signage

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Someone asked: "What is the proper lettering size for a warning sign for a large propane tank, and how do I go about writing a SPCC?"

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I responded: "Trigonometry tells us that .017453 in/ft x D ft = height of 20/20 letter in inches . So, in order for lettering to be visible at D = 300 feet, for instance, letters about 5.25 inches high are needed. ANSI Z535.2-2002 indicates that minimum letter height for the signal word (e.g., Danger) shall be one unit of height for every 150 units of safe viewing distance. Minimum letter height for other words on the sign shall be one unit of height for every 300 units of safe viewing distance. Therefore, if D = 300 feet is "safe," then "DANGER" should be 2 feet high and "No smoking within 100 feet" should be 1 foot for the signs mounted on the tank. (The barrier fencing signage, of course, is much smaller). {I'd determine a starting point for the safe distance using CAMEO and ALOHA, reviewing the EIR, consulting with experts, etc.}

For a SPCC, see http://www.epa.gov/emergencies/docs/chem/storage.pdf . CFATS may also apply ( see https://www.dhs.gov/files/laws/gc_1166796969417.shtm )."