The employer shall post in a conspicuous place in every workroom where any work or process included in section two¹ is carried on, in every room where washing facilities are provided, and in every dressing-room and eating-room, a notice of the known dangers arising from such work or process, and simple instructions for avoiding as far as possible such dangers. The Commissioner of Labor and Industry² shall prepare a notice containing the provisions of this act, and shall furnish free of cost a reasonable number of copies thereof to every employer included in section two, and the employer shall post copies thereof in the manner hereinbefore stated. The notices required in this section shall be printed in plain type, on cardboard, and shall be in English and in such other languages as the circumstances may reasonably require. The contents of such notices shall be explained to every employee by the employer, when the said employee enters employment in such work or process; interpreters being provided by the employer when necessary to carry out the above requirements.