Although there are exceptions for the following classes, you should not smoke in close proximity to any dangerous material. No smoking is permitted within 25 feet of classes 3 and 2.1. (flammable materials and gases). No smoking or holding a lighted smoking instrument such as a cigar or pipe is permitted within 25 feet of classes 1, 3, 4, or 4.2. (explosives, flammable liquids or solids, or spontaneously combustible materials).