Planning; Adverse Atmospheres; Entering Manholes - Teledyne 5800 Installation And Operation Manual

Isco 5800 Refrigerated Sampler
Appendix B General Safety Procedures
B.2 Planning
B.3 Adverse Atmospheres
B.4 Entering Manholes
B-2
This applies to hand tools as well as stones, gravel and
other objects.
• 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.
Advance planning should include arrangements for test
equipment, tools, ventilating 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.
[Refer to the table of Hazardous Gases at the end of this
appendix.] Before workers enter a manhole, tests should be made
for explosive atmosphere, 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
the way down the manhole.
Whenever adverse atmosphere is encountered, forced ventilation
must be used to create safe conditions. After the ventilating
equipment 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 manhole should be
assumed to contain an unsafe atmosphere and forced ventilation
must be provided. It should never be assumed that a manhole is
safe just because there is no odor or the manhole has been
entered previously.
Since the to p of the manhole is usuall y f lush w ith the
surrounding surface, there may not be anything for the person
who is entering the manhole to grab on to steady himself.
Persons who are entering manholes should not be permitted to
carry anything 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 entering 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 downward, the feet can engage a rung, and the back
can rest against the opposite side of the opening. If there is any
doubt about the soundness of the manhole steps, a portable
ladder should be used.
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