Section R. 408.11221 - Cylinder markingRule 1221.
(1) Compressed gas cylinders shall be legibly marked, for the purpose of identifying the gas content, with either the chemical or trade name of the gas. Such marking shall be by means of stenciling, stamping, or labeling and shall not be readily removable. Whenever practical, the marking shall be located on the shoulder of the cylinder.(2) Unlabeled cylinders shall not be used.(3) Empty cylinders shall be so marked at time of depletion.Mich. Admin. Code R. 408.11221