2370                                               LAWS OF MARYLAND                         [Ch. 864

for this purpose; and

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

(f) (1) Deficiency of oxygen and excess of carbon
dioxide. — Air in mines in which workers work or travel
shall be improved if it contains less than 19.5 percent
oxygen, more than 0.75 percent carbon dioxide, or is
contaminated with any noxious or poisonous gas.

(2)    Excess methane.—Generally. If the air
immediately returning from a split that ventilates any
group of active workings contains more than [1.0] 1
percent methane, as determined with a permissible flame
safety lamp, by air analysis or by other recognized means
of accurate detection, the ventilation shall be improved.

(3)   Excess methane returning from a split.—If the
air immediately returning from a split contains 1.5
percent methane, a dangerous condition exists and the
workers shall be withdrawn from the mine or its affected
portion. Power shall be cut off from the mine or its
affected portion until the dangerous condition has been
corrected.

(4)   Accumulation of methane.—Blasting may not be
done at any working face or other place where methane has
accumulated and is likely to attain an explosive mixture.
The workers shall be removed from each working face or
place until the condition has been corrected.

(5)   Methane in face region.—If the methane content
of air in any face operation exceeds [one] 1 percent at
any point not. less than 12 inches from the roof, face, or
rib, as determined by a permissible methane detector, a
permissible flame safety lamp, or chemical analysis, the
workers shall be removed from the affected area until the
condition has been corrected by improving the
ventilation.

7-4 30.

(a) Unless a surface transformer is isolated by
elevation at least [eight] 8 feet above the ground, it
shall be enclosed in a transformer house or surrounded by
a suitable fence at least [six] 6 feet high. If the
enclosure is metal, it shall be grounded effectively.
The gate or door to the enclosure shall be locked at all
times, unless an authorized person is present.

(e) Trolley and direct and alternating current
feeder wires shall be installed as follows: