1054 LAWS OF MARYLAND. [CH. 437

The space between men riding on a belt line shall be
not less than 5 feet.

Loading and unloading stations shall be illuminated
properly.

An official or some other person designated by the mine
foreman shall supervise the loading and unloading of belts
and man-trips.

97. No person shall travel on foot to or from his work
on any slope, plane or haulage road, unless no other roads
are provided or available for that purpose, and then only
at such times as permitted by the mine foreman. No
person except officials and repairmen shall be permitted
to travel on slopes or planes while cars are in motion
thereon.

98. In every such mine wherever the condition of grade,
weight to be moved, and distance of movement of any of
them render the placing of. mine cars liable to physically
injure the miners if they are required to place such cars
by their own exertions, the Bureau may by general regu-
lation require that such cars, by mechanical or animal
power, be placed at such point in the heading, room or
other excavation where the miners are at work as shall
be convenient without being further moved for loading.

VENTILATION AND MINE GASES

99. Main fans (a) Mines shall be ventilated by means
of main fans which shall be installed on the surface in
fireproof housings, situated not less than 15 feet from
the nearest side of the mine opening, and be equipped with
fireproof air ducts and ample pressure-relief or explosion
doors, provided, however, that in mines where the air is
of such purity that it contains not less than 19. 5 percent
of oxygen and not more than 0. 75 percent of carbon diox-
ide, a fan shall not be required, but if the Bureau of Mines
shall determine that the purity of the air is below these
standards, the Bureau shall order the installation of a fan
or fans or other mechanical devices to insure the purity of
the air prescribed herein. However, present fans that are
offset any distance from the mine opening need not be
moved if they otherwise comply with the provisions of this
Section.

(b) In lieu of requirements for the location of the fan
and the pressure-relief or explosion doors, the fan may be
directly in front of, or over, the mine opening, provided the
opening is not in direct line with possible forces coming out
of the mine if an explosion occurs, and provided further