The operator shall employ a certified strip pit mine foreman for every mine except those mines in which no more than three (3) persons including the operator are employed, in which case one (1) man must have at least the status of a certified shot firer. The mine foreman shall have full charge of all workings and of all persons employed therein in order that all the provisions of this act, so far as they relate to his duties, shall be complied with and the regulations prescribed for each class of workmen under his charge shall be carried out in the strictest possible manner.