Every person who shall light a pipe, cigar or cigarette in, or who shall enter with a lighted pipe, cigar or cigarette, any factory, mercantile establishment, mill or workshop in which is posted in a conspicuous place over and near each principal entrance a notice in plain English letters, stating that no smoking is allowed in such building, shall be guilty of a misdemeanor, and, upon conviction thereof, shall be fined not less than $20 nor more than $100 for each separate offense.