2-13. CLEANING AND GAS FREEING OF CARGO TANKS - Continued.
Provisions must be made for disposal of waste water pumped from tanks. It must not be dumped into
harbor or coastal waters. It may be temporarily pumped into another tank and later disposed of.
Preferably, it should be pumped into a shore waste line or another barge.
b. After washing, ventilate the tank with a windsail. Keep hatches open for ventilation. The tanks must be certified
gas free before any work is performed in them.
2-14. PRECAUTION ON ENTERING CARGO TANKS.
Petroleum vapors are both toxic and explosive. In sufficient concentration petroleum vapor may cause
death within five minutes. In lesser concentrations, irritation of the eyes, severe headache, and mild
exhilaration may be experienced. Tanks which are not ventilated and have remained empty for a while
may be depleted in oxygen due to rusting. The oxygen content may not be enough to support life.
a. Extreme caution must be exercised if it becomes necessary to enter a cargo tank that is not known to be gas free
and certified safe.
b. If it is absolutely necessary to enter a tank that has not been certified gas free, observe the following precautions:
(1) Ventilate the tank with windsail or mechanical blower.
(2) Secure a harness and a safety line to the person entering the tank.
(3) Assign an observer on deck with no other duty except to watch the person in the cargo tank and assist the
person from the tank if necessary.
(4) The person entering the cargo tank should carry no tools, flashlight, or anything capable of producing a
c. Use the following equipment if available:
(1) Portable testing apparatus to measure gas concentration.
(2) Flame safety lamp to determine oxygen content but only if gas concentration is within safe limit.
(3) Oxygen breathing apparatus if oxygen level is low and gas concentration is within safe limit.