151
6700SR Refrigerated Sampler
The safety of the personnel who use the 6700 is
a critical consideration. The following proce-
dures, applicable to working in and around
manholes and sewers, are those used by Black
& Veatch, a respected consulting firm, and are
published here by their kind permission
“Field personnel must keep safety uppermost
in their minds at all times. When working
above ground, rules of common sense and
safety prevail. However, when entering man-
holes, strict safety procedures must be
observed. Failure to do so could jeopardize not
only your own life, but also the lives of other
crew members.
“1.
Hazards
. There are many hazards con-
nected with entering manholes. Some of the
most common hazards are:
“
Adverse Atmosphere
. The manhole may
contain flammable or poisonous gases or the
atmosphere may be deficient in oxygen. Forced
ventilation may be necessary.
“
Deteriorated Rungs
. Manhole steps may be
corroded and not strong enough to support a
man. It may be difficult to inspect the rungs
because of poor lighting.
“
Traffic
. Whenever manholes are located in
the traveled way, barricades and warning
devices are essential to direct traffic away from
an open manhole.
“
Falling Objec
t. Items placed near the man-
hole opening may fall and injure a worker in
the manhole.
“
Sharp Edges
. Sharp edges of items in or near
a manhole may cause cuts or bruises.
“
Lifting Injuries
. Unless proper tools are
used to remove manhole covers, back injuries
or injuries to hands or feet may result.
“2.
Planning
. Advance planning should include
arrangements for test equipment, tools, venti-
lating equipment, protective clothing, traffic
warning devices, ladders, safety harness, and
adequate number of personnel. Hasty actions
may result in serious injuries. Time spent in
the manhole should be kept to a minimum.
“3.
Adverse Atmosphere
. [Refer to Table 15,
Hazardous Gases, on page 154 at the end of
this appendix.] Before workers enter a man-
hole, tests should be made for explosive atmo-
sphere, presence of hydrogen sulfide, and
oxygen deficiency. Combustible or toxic vapors
may be heavier than air, so the tests on the
atmosphere must be run at least 3/4 of the way
down the manhole.
“Whenever adverse atmosphere is encoun-
tered, forced ventilation must be used to create
safe conditions. After the ventilating equip-
ment has been operated for a few minutes, the
atmosphere in the manhole should be retested
before anyone enters the manhole.
“When explosive conditions are encountered,
the ventilating blower should be placed upwind
to prevent igniting any gas that is emerging
from the opening. When a gasoline engine
blower is used, it must be located so that
exhaust fumes cannot enter the manhole.
“If testing equipment is not available, the man-
hole should be assumed to contain an unsafe
atmosphere and forced ventilation must be pro-
vided. It should never be assumed that a man-
hole is safe just because there is no odor or the
manhole has been entered previously.
“4.
Entering Manholes
. Since the top of the
manhole is usually flush with the surrounding
surface, there may not be anything for the per-
son who is entering the manhole to grab on to
steady himself. Persons who are entering man-
holes should not be permitted to carry any-
thing in their hands as they enter the manhole,
to ensure that their hands will be free to hold
on or grab if they slip. A good method for enter-
ing a manhole is to sit on the surface facing the
manhole steps or ladder, with the feet in the
hole and the arms straddling the opening for
support. As the body slides forward and down-
ward, the feet can engage a rung, and the back
can rest against the opposite side of the open-
ing. If there is any doubt about the soundness
of the manhole steps, a portable ladder should
be used.
“A person should never enter a manhole unless
he is wearing personal safety equipment,
including a safety harness and a hard hat. Two
persons should be stationed at the surface con-
tinuously while anyone is working inside a
manhole, to lift him out if he is overcome or
injured. One man cannot lift an unconscious
man out of a manhole.
Appendix C General Safety Procedures
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