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Precautions Prior to Entering Enclosed Spaces
An enclosed space is one that, by design, has limited openings for entry and exit, unfavorable natural ventilation that could contain or produce dangerous air contaminants, and is not intended for continuous employee occupancy.
Enclosed spaces include but are not limited to storage tanks, compartments of ships, process vessels, wells, void spaces, boilers, ventilation and exhaust ducts, tunnels.
The hazards associated with enclosed spaces can cause serious injury and death to workers. Two major factors lead to fatal injuries in enclosed spaces:
1. Failure to recognize and control the hazards associated with enclosed spaces and
2. Inadequate or incorrect emergency response.
The emergency response is usually a spontaneous reaction to an emergency and can lead to multiple fatalities.
Enclosed spaces may be classified into two categories:
1. Open-topped enclosures with depths that restrict the natural movement of air (e.g., types of tanks, cargo holds) and
2. Enclosures with limited openings for entry and exit (e.g., tanks, ducts, boilers).
The hazards found in any enclosed space are determined by the material being stored or used, by the process taking place inside the space, and by the effects of the external environment. Worker entry into enclosed spaces may occur during construction activities or during frequent necessary functions such as inspection, repair or maintenance.
An enclosed space:
– Has limited or restricted means of entry or exit
– Is large enough for an employee to enter and perform assigned work
– Is not designed for continuous occupancy.
While there are many enclosed spaces on a ship, the ship itself can be considered to be an enclosed space, when locked within, without motive power and at the middle of an ocean, away from the comfort of land. You can get abandoned together with the ship and it could become difficult to get away from a sinking ship, for example. But even without that larger scope, the discussion on enclosed space operations remains demanding and you need regular practice drills and what-if scenarios to make yourself ready and act in a safe manner.
Dangers associated with enclosed spaces
What Are the Hazards Involved in Entering and Working in Enclosed Spaces?
Many workplaces contain spaces configured in such a way to be considered “enclosed”. Enclosure itself may pose entrapment hazards. Working in an enclosed space may keep employees closer to hazards. For example, enclosed, limited access or restricted airflow can result in hazardous conditions that would not arise in an open workplace.
Hazardous Atmospheres
Many substances have short-term exposure limits, in addition to 8-hour time-weighted average exposure limits. The permit-required enclosed space rule is intended to protect against short-term acute hazards. Exposures at or below the permissible exposure limits do not fall under the permit-required enclosed space rule. Other standards address a broader range of health and safety concerns. Any substance that is not capable of causing death, incapacitation, impairment of ability to self-rescue, injury or acute illness due to health effects is not covered by the rule.
The atmosphere in an enclosed space may be extremely hazardous because of the lack of natural air movement. This characteristic of confined spaces can result in:
1. Oxygen-deficient
2. Flammable or
3. Toxic atmospheres.
Oxygen-Deficient Atmospheres
An oxygen-deficient atmosphere has less than 19.5 percent available oxygen (O₂). When oxygen levels drop below 17 percent, there is increased breathing volume, accelerated heartbeat and a deterioration of night vision, which is usually not noticeable. Oxygen atmospheres with 14 to 16 percent oxygen contribute to poor muscular coordination, rapid fatigue and intermittent respiration. At 6 percent oxygen, there is a rapid loss of consciousness and death in minutes.
Any atmosphere with less than 19.5 percent oxygen should NOT be entered without an approved self-contained breathing apparatus or an approved supplied air breathing apparatus.
The oxygen level in a confined space can decrease because of the type of work being done, such as welding, cutting or brazing, or it can be decreased by certain chemical reactions (rusting) or through bacterial action (fermentation).
The oxygen level is also decreased if oxygen is displaced by another gas, such as carbon dioxide, argon, helium or nitrogen. Total displacement of oxygen by another gas, such as carbon dioxide, will result in unconsciousness, followed by death.
Toxic Atmospheres
Because air cannot freely move in and out of enclosed spaces due to the design and configuration, the atmosphere inside an enclosed space can be very different from the atmosphere outside. Deadly gases may be trapped inside, particularly if the space is used to store or process chemicals or organic substances that may decompose. There may not be enough oxygen inside the enclosed space to support life, or the air could be so oxygen-rich that it is likely to increase the chance of fire or explosion if a source of ignition is present.
Toxic atmospheres can be caused by the following:
1. The product stored in the space. The product may contain a toxic component, which could be absorbed into the walls and have the potential for release depending on the use of the space.
2. Examples of the type of work being performed in an enclosed space include welding, cutting, brazing, painting, scraping, sanding and degreasing. Toxic atmospheres are generated in various processes. For example, cleaning solvents are used in many industries for cleaning/degreasing. The vapours from these solvents can build up to toxic levels in an enclosed space.
General/Physical Hazards
In addition to the areas discussed above, evaluation of a confined space should consider the following potential hazards:
1. Temperature Extremes
Extremely hot or cold temperatures can present problems for workers. For example, when possible, a steam tunnel should be allowed to cool before entering.
2. Engulfment Hazards
Loose granular material stored in bins and hoppers, such as grain, sand, coal or similar material, can engulf and suffocate a worker. The loose material can crust over, or bridge over, in a bin and break loose under the weight of a worker.
3. Noise
Noise within an enclosed space can be amplified because of the design and acoustic properties of the space. Excessive noise can not only damage hearing and reduce reaction time to hazards but can also affect communication. This can cause a shouted warning to go unheard.
4. Slick/Wet Surfaces
Slips and falls can occur on a wet surface, causing injury or death to workers. Spaces that have an internal configuration, inwardly converging walls, or a floor that slopes downward and tapers to a smaller cross-section, increase the hazards of slipping and falling. Different material contained in the space may react differently in a wet environment. A wet surface will also increase the likelihood for and effect of electric shock in areas where electrical circuits, equipment and tools are used.
5. Falling Objects
Workers in enclosed spaces should be mindful of the possibility of falling objects, particularly in spaces that have topside openings for entry and where work is being done above the worker.
6. Lack of Lighting or Poor Lighting
Working within an enclosed space, which is normally dark under operating conditions or, at the most dimly lit will require additional illumination before work can start. This comes in the form of intrinsically safe lighting which are flash-proof. These lights help the crew to do their duty within the tank etc, and in the absence of those or when they may go off without notice, could create accidental slips and panic inside the space and to be avoided at all costs.
Procedures prior to entry into an enclosed/confined space
1. Testing the Atmosphere
The atmosphere in an enclosed space may be hazardous due to:
– Low oxygen levels;
– Flammable or explosive concentrations of gases, vapours or dusts; or
– Toxic levels of gases and vapours.
Therefore, the air in an enclosed space must be tested first for oxygen, then for flammable or combustible gases and vapors, and then for toxic gases and vapors.
It is important to understand that some gases and vapors are heavier than air and will settle to the bottom of a confined space. Also, some gases are lighter than air and will be found around the top of the confined space. Therefore, it is necessary to test all areas (top, middle, bottom) of a confined space with testing instruments that are calibrated in accordance with the manufacturer’s recommendations to determine what atmospheric conditions are present.
If testing reveals oxygen-deficiency or the presence of toxic gases or vapors, the space must be ventilated and retested before workers enter. If ventilation is not possible and entry is necessary (for emergency rescue, for example), workers must have appropriate respiratory protection.
Never trust your senses to determine if the air in a confined space is safe! You cannot see or smell many toxic gases and vapors, nor can you determine the level of oxygen present.
2. Ventilation
Ventilation by a blower or fan may be necessary to remove harmful gases and vapors from a confined space. There are several methods for ventilating a confined space. The method and equipment chosen are dependent upon the size and configuration of the confined space openings, the gases to be exhausted (for example, are they flammable?), and the source of makeup air.
For example, under certain conditions where flammable gases or vapors have displaced the oxygen but are too rich to burn, forced air ventilation may create a dangerous condition by diluting them until they are within the explosive range. It may be necessary to use inert gases (such as carbon dioxide, nitrogen, argon, etc.) to reduce flammable gases or vapors to safe levels within the confined space. However, the space should be well-ventilated and retested before a worker may enter.
A common method of ventilation requires a large hose, one end attached to a fan and the other lowered into a manhole or opening. For example, a manhole would have the ventilating hose run to the bottom to blow out all harmful gases and vapors. The air intake should be placed in an area that will draw in fresh air only. An air supply taken next to a vehicle or compressor exhaust system could draw in one hazardous gas while exhausting another. Ventilation should be continuous where possible, because in many confined spaces the hazardous atmosphere will accumulate again when the flow of air is stopped. Periodic testing must be conducted to ensure that the atmosphere inside the confined space is safe. Remember that any testing information concerning the space has to be made available to the entrant or the entrant’s authorized representative.
3. Permit System
A permit, signed by the entry supervisor (maybe Chief Officer on a ship) and verifying that pre-entry preparations have been completed and that the space is safe to enter, must be posted at entrances or otherwise made available to entrants before they enter a permit space.
The duration of entry permits must not exceed the time required to complete an assignment. Also, the entry supervisor must terminate entry and cancel permits when an assignment has been completed or when conditions that are not allowed may arise. New conditions must be noted on the cancelled permit and used in revising the permit space program. The standard also requires the employer to keep all cancelled entry permits for at least one year or as stipulated in company Safety Manual.
Entry Permits
Entry permits must include the following information:
– Test results
– Tester’s initials or signature
– Name and signature of supervisor who authorizes entry
– Name of permit space to be entered, authorized entrant(s), eligible attendants and individual(s) authorized to be entry supervisor(s)
– Purpose of entry and known space hazards
– Measures to be taken to isolate permit spaces and to eliminate or control space hazards, i.e., locking out or tagging of equipment and procedures for purging, making inert, ventilating and flushing permit spaces
– Name and telephone numbers of rescue and emergency services
– Date and authorized duration of entry
– Acceptable entry conditions
– Communication procedures and equipment to maintain contact during entry
– Additional permit(s), such as for hot work, that have been issued to authorize work in the permit space
– Special equipment and procedures, including personal protective equipment, alarm systems and rescue equipment
– Any other information needed to ensure employee safety
Authorized Entrant’s Duties
– Know space hazards, including information on the mode of exposure (e.g., inhalation or dermal absorption), signs or symptoms, and consequences of the exposure
– Use appropriate personal protective equipment properly (e.g., face and eye protection, and other forms of barrier protection such as gloves, aprons and coveralls)
– As necessary, maintain communication (i.e., telephone, radio, visual observation) with attendants to enable the attendant to monitor the entrant’s status as well as to alert the entrant to evacuate
– Exit from permit space as soon as possible when ordered by an authorized person, when the entrant recognizes the warning signs or symptoms of exposure exist, when a prohibited condition exists, or when an automatic alarm is activated
– Alert the attendant when a prohibited condition exists or when warning signs or symptoms of exposure exist
Attendant’s Duties
– Remain outside permit space during entry operations unless relieved by another authorized attendant
– Perform non-entry rescues when specified by employer’s rescue procedure
– Know existing and potential hazards, including information on the mode of exposure, signs or symptoms, consequences of the exposure, and their physiological effects
– Maintain communication with and keep an accurate account of those workers entering the permit-required space
– Order evacuation of the permit space when a prohibited condition exists, when a worker shows signs of physiological effects of hazard exposure, when an emergency outside the confined space exists, or when the attendant cannot effectively and safely perform required duties
– Summon rescue and other services during an emergency
– Ensure that unauthorized persons stay away from permit spaces or exit immediately if they have entered the permit space
– Inform authorized entrants and entry supervisor of entry by unauthorized persons
– Perform no other duties that interfere with the attendant’s primary duties
Entry Supervisor’s Duties
– Know space hazards including information on the mode of exposure, signs or symptoms, and consequences of exposure
– Verify emergency plans and specified entry conditions such as permits, tests, procedures and equipment before allowing entry
– Ensure that determinations and supporting data from required tests are documented and are made available to each employee who enters the permit space or that employee’s authorized representative
– Ensure that the entrant or the entrant’s authorized representative are afforded the opportunity to observe any testing of the confined space prior to and during the operation
– Terminate entry and cancel permits when entry operations are completed or if a new condition exists
– Take appropriate measures to remove unauthorized entrants or persons who attempt to enter
– Ensure that entry operations remain consistent with the entry permit and that acceptable entry conditions are maintained
Rescue
– Over 50 percent of the workers who die in confined spaces are attempting to rescue other workers.
– Rescuers must be trained in and follow established emergency procedures and use appropriate equipment and techniques (including lifelines, respiratory protection and standby persons). Steps for safe rescue should be included in all confined space entry procedures. Rescue procedures should be well planned, and drills should be frequently conducted on emergency procedures.
– An unplanned rescue, such as when someone instinctively rushes in to help a downed co-worker, can easily result in a double fatality or even multiple fatalities if there is more than one would-be rescuer.
Remember: An unplanned rescue could be your last.
– A standby person should be assigned to remain on the outside of the confined space and be in constant contact (visual or speech) with the workers inside. The standby person should not have any other duties but to serve as standby and know who should be notified in case of emergency. Standby personnel should not enter a confined space until help arrives, and then only with proper protective equipment, lifelines, and respirators.
The employer has overall responsibility for employee safety.
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