This sign is often used for Acetone, Ethanol and Gasoline.
This NFPA sign measures 14" tip-to-tip (but when you measure the sign as a square, they are 10" long on each dimension). Each number is about 3" high – which using common visibility benchmarks, should be legible from 100-150' away. This gives firefighters plenty of time (and space) to safely gauge their proper response to an emergency, spill or fire.