refers to an area with limited means of entry and
exit that is large enough for a person to fit into
but is not designed for occupancy.
any place, including any vessel, tank, container,
pit, bund, chamber, cellar or any other similar
space which, by virtue of its enclosed nature,
creates conditions that give rise to a likelihood of
an accident, harm or injury.
Hazards in a confined space often include
suffocation by gases which may be present but
not visible, or submersion in liquids or free-
flowing granular solids (for example, grain bins)
Confined space generally recognized as:
has limited or restricted means of entry or
is large enough for a person to enter to
is not designed or configured for continuous
has the potential for a significant hazard to
According to the OSHA (USA), a permit-required
confined space (permit space) has the three
characteristics listed above (which define a
confined space) and one or more of the
Contains or has the potential to contain a
Contains a material that has the potential for
engulfing the entrant
Has an internal configuration that might cause an
entrant to be trapped or asphyxiated by inwardly
converging walls or by a floor that slopes
downward and tapers to a smaller cross section
Contains any other recognized serious safety or
Factories and Machinery ( Safety , Health and Welfare)
13. (1) “Where any work has to be done inside any chamber,
tank vat, pit, pressure or other vessel or other confined space in
which dangerous fumes are liable to be present to such extent
as to involve risk to any person being overcome thereby, such
confined space shall, unless there is other adequate means of
egress, be provided with a manhole: such manhole should be
rectangular, oval or circular in shape, and shall not be less than
sixteen inches wide or not less than eighteen inches in diameter
Factories and Machinery ( Safety , Health and Welfare) Regulations 1970
13. (2) “ no person shall be required or permitted to enter any confined
a. all practicable steps have been taken to removes any fumes which may
present and to prevent any ingress in fumes;
b. It has been ascertained by a suitable test that the confined space is
free from dangerous fumes:
Provided that where such test cannot be carried out the person
entering the confined space shall wear an efficient respiratory protective
device suitable for the dangerous substance that may is to be expected
and a suitable safety belt with attached life line of adequate dimensions
leading to a convenient point outside the tank or vessel; and
a. a reliable and competent person is stationed at the entrance to the
tank or vessel to supervise the operations and to take such action as
may necessary in any emergency.
The most common hazard seen in confined
spaces is that of atmospheric hazards. This
involves 2 types of hazard which are toxic
hazard and explosive hazard.
These affect air quality and present
immediate hazards to health or life.
Acceptable atmospheric conditions must be
verified before entry, and must be monitored
continuously while the space is occupied.
The oxygen concentration, the presence of
toxic gases, and flammable material are the
three conditions that must be monitored.
1. Oxygen concentration is considered safe if
it is between 19.5% and 23.5% of the total
2. To protect against toxic gases,
contaminants should not exceed the
permissible exposure limits (PELs), which
are set by OSHA .
3. Work also cannot continue if the
concentration of a material reaches or
exceeds 10% of its lower explosive limit.
Even if a tank or similar vessel initially is
tested and found to contain breathable air, a
hazard can develop during operations inside
the tank if residues inside the tank can
release toxic gas or vapor when disturbed or
if accidentally ignited.
Steel water tanks may have dangerously low
oxygen concentration when the interior rusts.
Table 1: Percentage of oxygen in the air and it effect to
Another hazard related to confined space is
Caused by mechanical or physical obstruction
present in the confined space.
To ensure that a confined space is safe, some question
need to be asked and answer before allowing entry.
1. Are access and exit equipment such as ladders and
steps in good working condition?
2. Has the confined space been properly purged of the
toxic vapors and other toxic substances.
3. Are all lines that transport potentially hazardous
substances into or through the confined space turned
off and properly capped?
4. Are all moving equipment and moving parts of
equipment in the confined space shut down and locked
5. Has proper ventilation (natural or mechanical) been
1. Appointment of a supervisor
Supervisors should be given responsibility to make
sure that the necessary precautions are taken, to
check safety at each stage and may need to remain
present while work is underway.
2. Suitability of the worker
Experiences, training, claustrophobia, medical
Mechanical and electrical isolation of equipment is
essential if it could otherwise operate, or be
operated, inadvertently. If gas, fume or vapour could
enter the confined space, you need to isolate the
pipework. In all cases, a check should be made to
ensure isolation is effective.
4. Cleaning before entry.
5. Size checking
Is it big enough to allow workers wearing all the
necessary equipment to climb in and out easily,
and provide ready access and exit in an
6. Probation of ventilation
Improved ventilation, mechanical ventilation,
7. Testing of the inside air
8. Provision of special tools and lighting
Non-sparking tools, extra low voltage equipment
(less than 25V)
9. Provision of breathing apparatus
10. Preparation of emergency arrangements
11. Provision of rescue harness