1056 LAWS OF MARYLAND. [CH. 437

1. The fan motor shall be an enclosed type, the sur-
roundings of the fan fireproofed, and the fan installed and
located so as to prevent recirculation of air.

2. Passageway by the fan installation shall be by means
of an air lock, the doors of which shall have at least 30
square feet cross-sectional area and open automatically
when the fan stops operating.

3. In case of booster-fan stoppage, the procedure herein-
before contained in this Act with respect to stoppage of
main fans shall apply to the section of the mine affected.

4. Inspected at least twice each shift and provided with
a signal light, audible signal, or attended constantly.

(b) Blower fans with tubing used in gassy mines shall
be surrounded with safeguards as follows:

1. The fan shall be powered with a permissible driving
unit and installed on the intake-air side of the entrance of
the place to be ventilated not less than 16 feet from the
nearest rib.

2. The volume of air in which the fan is placed shall be
at least 21/2 times the manufacturers maximum rated ca-
pacity of the fan.

3. The fan and tubing shall be maintained in good
condition. The discharge end of the tubing shall be kept
within 35 feet of the face, and not more than 300 feet of
the tubing shall be extended from the fan.

4. Places ventilated by means of blower fans shall be
examined for methane by a certified official or other com-
petent person designated by the mine foreman before the
fan is started at the beginning of the shift and after the
interruption of fan operation for 5 minutes or more during
the shift.

5. Accumulations of methane shall not be moved by
means of a blower fan and tubing; only line brattice shall
be used for this purpose.

6. The fan and tubing shall be inspected at least twice
during each working shift.

101. (a) Volume of Air. The main intake air current
shall when necessary be divided into splits utilizing air
crossings, where needed, so as to ventilate all parts of the
mine effectively.

The number of men on a split shall be limited to 75.