Guidelines to Safe Working in Confined Space
What is Confined Space?
Confined space is a space which has limited accessibility, unfavorable natural
ventilation and it is not design for continuous occupancy. Confined spaces
include, but not limited to storage tanks, silos, sewers, compartment of
ships, pits, tunnels, pipelines, vats, boilers and enclosed drains.
Storage Tank
Septic Tank
Silo
Boiler
Manhole
Pipeline
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Guidelines to Safe Working in Confined Space
Hazards in Confined Space
a. Lack of Oxygen
21%
12%
10%
15%
19.5%
Oxygen Enriched
1
No
2
1
Oxygen
Concentration
(%)
< 10%
2
10% - 12%
3
12% - 15%
4
15% - 19.5%
5
21%
3
4
5
Health Effect
Inability to move. Fainting almost immediate.
Loss of consciousness. Convulsions. Death.
Very poor judgment and coordination. Impaired
respiration that may cause permanent heart
damage. Possibility of fainting within a few
minutes without warning. Nausea and vomiting
Poor judgment. Faulty coordination. Abnormal
fatigue upon exertion. Emotional upset.
Impaired thinking and attention. Increased pulse
and breathing rate. Reduced coordination.
Decreased ability to work strenuously. Reduced
physical and intellectual performance without
awareness.
Safe to enter
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Guidelines to Safe Working in Confined Space
b. Flammable Atmosphere
Flammable atmosphere is caused by flammable fuels, paint, cleaning
solvents, combustible dust (such as metal), naturally occurring reactions
that produce methane gas, or hydrogen from boiler cleaning or battery
charging. Different gas has different flammable ranges. An explosive will
result if source of ignition introduce into a space which have flammable
atmosphere.
Oxygen
Explosion
Fire
Gas,
Vapor,
Fuel
Ignition
Excessive Oxygen in the atmosphere can cause flammable material to burn
easily when ignited. Therefor never ventilate a confined space with oxygen.
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Guidelines to Safe Working in Confined Space
c. Toxic Atmosphere
Toxic atmosphere comes from substances such as poisonous gases, fume,
vapor, mists, solid material and dust. It generated in various process;
1. Product Stores in Confined Space – product absorbed into the wall and
gives off toxic gas when removed or cleaned out. For example; sludge
removal from storage tank can release deadly Hydrogen Sulfide (H2S)
2. Work carry out in Confined Space – for example welding, grinding,
cutting, brazing, scrapping, painting and degreasing. Cleaning solvent
for industrial used for cleaning purpose contains vapor which is toxic.
3. Work in area adjacent to Confined Space – can produced toxicants
which enter and accumulate in Confined Space
d. Atmosphere Testing (Gas Testing)
Before entering a confined space, gas test must be conducted to identify
type of gases present. It is very important to know that some gases are
heavier and some are lighter. The heavier gas will settle at the bottom on
a confined space, for example Hydrogen Sulfide (H2S) and the lighter gas
will settle at the top of a confined space, for example Methane (CH4).
Therefore, it is necessary to conduct gas test in all areas (bottom, top,
middle) of a confined space using a proper gas detector with valid
calibration time. If testing result shows presence of toxic gas or oxygen
deficiency, the space must be ventilated and re-tested before workers
enter. If ventilation is impossible and entry is necessary, proper
respiratory must be provided.
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Guidelines to Safe Working in Confined Space
e. Ventilation
Ventilation may be necessary to remove harmful gasses from confined
space. You may also be able to increase the number of openings and
therefore improve ventilation. Mechanical ventilation may be needed to
make sure there is an adequate supply of fresh air.
f. Isolation
Isolation is a process by which a permit space is removed from service
and completely protected against the release of energy and material into
the space by such means as: blanking or blinding; misaligning or
removing sections of lines, pipes, or ducts; a double block and bleed
system; lockout or tagout of all sources of energy; or blocking or
disconnecting all mechanical linkages. If gas, fume or vapor could enter
the confined space, you need to isolate the pipework. In all cases, a
check should be made to ensure isolation is effective.
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Guidelines to Safe Working in Confined Space
g. Respiratory
Respiratory is a device which allows worker to work safely in a confined
space. 2 types of respirator commonly use while working in confined
space. Air purifying respirator which filter dangerous substances in the air
and air supplying respirator which known as Self Contained Breathing
Apparatus (SCBA) to provide breathing air (for example used by Rescuer)
Half mask respirator
Full face mask respirator
SCBA
h. Competent Person
Working in a confined space requires competent persons who has
undergone training acquiring knowledge, understanding and skills in
confined space
• Entry Supervisor (ES) – responsible to determine the acceptable entry
conditions
• Authorised Gas Tester (AGT) – responsible to test and interpret the
reading level of gaseous in confined space
• Authorised Entrant (AE) – worker who enter a confined space
• Standby Person (SP) – standby outside a confined space and must be in
constant contact with Authorised Entrant.
• Emergency Rescue Team – must be trained and equipped with rescue
knowledge to provide proper rescue technique and equipment to workers
inside confined space.
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Guidelines to Safe Working in Confined Space
i. Personal Protective Equipment (PPE)
Workers must be equipped with PPE before entering confined space.
Proper PPE is essential to protect worker from physical hazards, for
example falling on wet surface or falling down objects above head. PPE
includes hard hat, safety shoes, body harness, glove, safety glasses and
proper coveralls.
j. General/Physical Hazard




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Temperature – extreme temperature condition in confined space
can cause problems to the workers. For example, if the space is
steamed, it should be allowed to cool down before entry.
Engulfment – workers may encounter engulfment and suffocation
when enter and trapped in space containing liquid, powdered
material or fine flowable solid such as sand, grains, etc
Noise – excessive noise can affect hearing and communication
between the workers. For example, warning shouts by the workers
can go unheard.
Wet surface – slippery surface can cause falls and injuries. Some
cases it also can cause death due to falls or electrical shocked in
areas where electric equipment and tools are used
Falling Objects – workers should aware and alert of the possibility
of falling object when they work inside a confined space especially
when the opening in on top of them.
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Guidelines to Safe Working in Confined Space
For further information about Confined Space, please contact us at;
+603.5888.9444
+6019.214.0424
www.mydasafety.com
mydasafety
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