(3)If the atmosphere is clear, the leader shall, when passing the junction of two or more roadways, clearly indicate the route by means of arrow marks in chalk. If the atmosphere is obscure, the leader shall see that a life line is lead in from the fresh air base, and shall not allow any member of the team to move out of reach of that line; or, if that course is impracticable, he shall not proceed until every roadway branching of from the route is fenced across the whole opening.
