Introduction
Confined Space:
OSHA defines a Confined Space, as one that has limited or restricted means of entry or exit, is large enough for employees to enter and perform their work, and is not designed for continuous occupancy.
Permit-Required Confined Space (PRCS):
• Contains or could contain a hazardous atmosphere.
• Contains materials that have the potential for engulfing the entrant.
• Has an internal configuration such as that an entrant could be trapped or asphyxiated.
• Any other recognized safety hazards.
The following types of facilities are designated as confined
spaces:
1. Manholes
2. Sewer lines
or tunnels.
3. Storage
tanks
4. Silos
5. Underground
utility vaults and storage.
6. Boilers
7. Pipelines.
8. Pits
9. Wells.
There are two types of confined spaces:
Class, I confined space:
This is a permit-required confined
space (PRCS) which, because of the nature of hazards or the location of the
space, it is not feasible or possible to render space safe to enter without
proper respiratory protection. Authorized personnel entering this type of space
must wear appropriate supplied-air respiratory equipment.
Class II Confined space:
This is a permit-required confined
space, which, due to the nature of the potential hazard(s) or the location of space, can be rendered safe for an employee to enter without wearing
respiratory protection.
This can be accomplished through
work practice such as continuous ventilation and air monitoring of the space.
The following are some of the general categories of hazards,
which may be encountered in confined space:
• Atmospheric hazards.
• Mechanical and Electrical hazards.
• General Safety (means of access/egress, trips, slips falls, hot, cold, etc.)
• Engulfment hazard.
Atmospheric Hazard:
Atmospheric hazards cause the most
confined-space related deaths and injuries.
Atmospheric hazards generally
cannot be seen, in most cases, it is too dangerous to assume that the sense of the smell will serve as an “early warning system” air monitoring is usually required
if atmospheric hazards are suspected.
There are three general classes of atmospheric hazards:
• Oxygen deficiency
• Combustible / flammable materials
• Toxic gases
A.
Oxygen Deficiency:
1. Humans can survive for weeks without food,
without water, but only a few minutes without air.
2. Air contains a mixture of gases but is
composed primarily of nitrogen (78%) and oxygen (21%).
3. When levels of oxygen are reduced below
19.5%, serious health problem begins to occur very quickly.
4. Oxygen is consumed by a variety of
chemical processes:
o
Aerobic bacterial growth. (consume oxygen to live)
o
Oxidation of rusting of metals
o Combustion and displacement by other gases. (welding and cutting torches)
Flammable/Combustible Materials:
1. Flammable and combustible materials are of
an important concern with regards to fires and explosions in confined spaces.
(Hydrogen Sulfide, Carbon Monoxide,
acetylene, and Methane).
2. The proper mixture of fuel and oxygen
varies from gas to gas, but explosion range is defined as the area between the
lower explosive limits (LEL) and the upper explosive limits (UEL).
3. When the mixture is above the upper
explosive limits, it can readily move into flammable range with the addition of
dilution air.
4. Potential source of ignition that could be found in confined spaces include:
open flames, arcs from electrical equipment,
hot surfaces, static electricity, and frictional sparks.
Toxic Gas Hazards:
• Toxic or poisons gases present two kinds of risks in a confined space:
• Irritation
• Asphyxiation
Irritation:
Many gases, existing in low
concentration in the air, are irritating to the body’s respiratory and nervous
system.
Asphyxiants:
Any gases which when present in
high enough concentration causes the displacement of oxygen in the body.
Carbon Monoxide:
• Carbon Monoxide is one of the most common asphyxiants. It is produced by incomplete combustion of carbon fuels.
• Carbon Monoxide kills by chemically combining with the hemoglobin in red blood cells. This greatly reduces the ability of the blood to carry oxygen to the body tissues and brain cells.
Carbon Monoxide Exposure Effects
Hydrogen Sulfide:
• This gas even more toxic than Carbon Monoxide. It is produced through the decay of organisms and natural materials.
• This colorless gas has a characteristic rotten-egg odor at first smell; however after a short time the gas renders the olfactory nerve (which controls the sense of smell) ineffective, and the worker are no longer smells the substance, and yet it causes serious bodily harm in higher concentrations.
Hydrogen Sulfide Exposure Effects
Mechanical/Electrical Hazards:
The unexpected movement of
mechanical equipment or the unexpected discharge of electrical equipment in a
confined space presents a very hazardous situation for anyone within the space.
Commonly encountered equipment includes:
Blenders – Stirrers – mixers and agitators.
It is very important therefore to
ensure that all mechanical and electrical equipment is locked out and tagged
out when any work is to be performed in a confined space.
General Safety (Physical Hazards):
• Exposure to
higher environmental temperature during work activities.
• Exposure to
corrosive substances which could cause irritation to unprotected skin.
• Exposure to
rats and other pests living in the area.
• Poor or
inadequate illumination.
• Exposure to
noise from the use of hammers, hydraulic equipment.
• Slips and
falls on wet surfaces or resulting from broken or oxidized ladder rungs.
• Means of
access and egress.
• Improper
handling of tools and equipment can result in cuts and back injuries.
Engulfment:
• The movement or shifting of material within a confined space has been responsible for many injuries and fatalities.
• Of particular concern are loose, granular materials which can act like quicksand.
• Silos with grain inside are a prime example of this type of hazard.
• Possibility of engulfment by flooding while working in a storm sewer.
Written Entry Permit:
Before anyone can enter the permit – required confined space (PRCS) to work, there must be a written entry permit, which will list the following:
• Name/location of the Permit-Required Confined Space
• The purpose of entering the PRCS.
• Date and duration of the entry.
• Names of those entering.
• Names of those attending on the outside.
• Supervisor’s name.
• List of the expected hazard.
• Means by which you intend to isolate or control the hazards.
• Conditions under which you deem it acceptable to enter(level of oxygen, combustible, toxic materials, etc.)
• Test results of hazards in the atmosphere in the PRCS before and during the entry.
• Provisions for rescuing someone from the PRCS.
• Communication methods such as phones, radios, hand signals etc.
• To allow entering and attendants to communicate with each other.
• Equipment needed, including all the personal protective equipment, harness, alarm systems
• Other special precautions or considerations specific to a particular space.
Monitoring for Hazards in Confined Spaces:
Measuring and monitoring for
atmospheric hazards are one of the important things to remember when doing confined
space work.
1. Oxygen:
According to the standard, 19.5 %
is the minimum and 23.5% is the maximum range for oxygen in PRCS.
2. Combustibles:
Measure the percent of LEL and
according to the standard, the acceptable level for any combustible is at or
below 10% of its LEL.
3. Toxic:
Measure the concentration of toxic
substances that might be available and compare the same with TLV.
The entrant:
No one can enter a permit-required
confined space (PRCS) unless he is authorized. That means he has to be
thoroughly trained and checked out by his supervisor, so he will know:
• The hazards present in the space.
• How to recognize symptoms of exposure to hazards.
• How to maintain contact with the attendants on the outside.
• What personal protective equipment, retrieval lines, and harnesses he will need to stay safe in the space.
• To leave the space if he thinks he is in danger or if an alarm goes off.
The Attendant:
Work in Permit-Required Confined
Space will be monitored by an attendant who has been trained to:
• Keep constant count of every person in the space.
• Keep in contact with the workers in the space.
• Recognize and monitor hazards.
• Order evacuation if anything inside or outside the space looks dangerous for the workers inside.
• Call for help from a trained emergency response team if anyone has to be rescued from the space.
Entry Procedure:
Once the initial tests are completed and determined to be within acceptable limits, work may proceed utilizing the following precautions:
• At least two, and preferably three, employees will conduct all work operations in a confined space. One employee will remain outside of the space to be available in case of an emergency.
• This individual must be in direct communication with the other workers in the confined space, as well as have the capability to reach emergency response personnel.
• A portable blower must be used at all times during confined space work activities to purge the area of possible contaminated air.
• The blower intake must be located outside of the confined space and away from any operating internal combustion engine to ensure that fresh air is being supplied.
• Continuous monitoring of the atmosphere inside the confined space, and at any time the monitoring devices indicate the presence of toxic or flammable gases, or a decreased level of oxygen, employees are to evacuate the space at once.
• Each worker in the space shall wear a safety harness attached to a tripod located outside of the confined spaces.
Emergency and Rescue Procedures
If someone has to be rescued from a
confined space, that is the job of the rescue team.
The rescue team will know how to :
• Close off the area
• Remove victims with harnesses or rescue equipment.
• Use oxygen, CPR, and other rescue and first-aid techniques and equipment.
• They will enter the confined space wearing an SCBA respiratory system.
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