Section 7042 - (11-3). Construction of Metal Ladders for Underground Use(a) Metal ladders shall be substantially constructed. Side rails shall have at least equal strength as that of No. 1 Select Douglas Fir, 2 inches by 4 inches in cross section.(b) Steps shall be secured to the side rails in such manner as to prevent them from coming loose.(c) Round ladder steps shall be at least 1-inch outside diameter. The steps of metal ladders shall be smooth and free of ribs or projections.(d) The distance between the tops of the steps of a ladder shall not exceed 14 inches and shall not vary more than 1 inch in any one ladderway.(e) Ladders shall be constructed so there is at least 10 inches clear space between the side rails.(f) Metal ladders and ladder fasteners for use where exposed to corrosive waters or corrosive mine atmosphere shall be constructed of materials that are resistant to corrosion of the type to which they are exposed.Cal. Code Regs. Tit. 8, § 7042