Section 652.040 - Maximum working hours in mines; exceptions(1) No person who operates any underground mine yielding gold or silver or copper or lead or other metal shall permit or require any person to work in such underground mine for more than eight hours in any 24 hours. The hours for such employment or work day shall be consecutive excluding, however, any intermission of time for lunch or meals.(2) In the case of emergency, where life or property is in imminent danger, persons may work in such underground mines for a longer time during the continuance of the exigency or emergency. This section does not apply to mines in their first stages of development, such as tunnel work to a length of 200 feet, or shaft work to a depth of 150 feet, or to any surface excavation.