(b) At permanent locations, such as bulldozing chambers, main grizzlies, draw points, and other control points where blasting is done throughout the working shift in the regular course of the work, employees shall be protected by one or more of the following, as necessary:

1. (1) A ventilation system that carries dust, smoke, and gases directly into the return air without circulation through any active working place.
2. (2) A system of water sprays that will blanket the area with a fine spray or mist during blasting, and long enough thereafter that the dust, smoke, and gases are allayed.
3. (3) Removal of employees from all areas of contamination until the atmosphere is reasonably free of dust, smoke, and gases.

(e) If the amount of explosive used or the frequency of secondary blasting is such that serious contamination of active working places is apt to occur, employees in such places shall be removed to the fresh air side of the blast area.

Such employees shall not be required or permitted to return to their working places until the atmosphere is reasonably free of dust, smoke, or gases.