Confined space may be defined as a place where the means of entry or exit are restricted because of location, design, construction or contents. It may include tanks, tankers, tunnels, silos, sewers, flues, pipelines, sea containers or vessels.
The main hazards encountered in confined spaces are fire or explosion, asphyxiation, toxicity, drowning in liquids or free flowing solids and injury or death if mechanical equipment within the confined space is inadvertently turned on while someone is still inside. These hazards are due to the presence of hazardous gases, vapours, fumes, dusts or the creation of an oxygen-deficient or oxygen-rich atmosphere.
Confined space fatalities
• 65% of all fatalities are due to air quality problems
• 100% of fatalities at 139 sites in 17 states in a two year period had one thing in common - no detector instruments or powered ventilation
• 29% of all people who died were supervisors
• 60% of all who died were rescuers • 25% died in spaces ‘ready to kill’
Is working in a confined space hazardous ?
Statistics show many workers are injured and killed each year while working in confined spaces. An estimated 60% of the fatalities have been among the would-be rescuers. A confined space can be more hazardous than regular workspaces for many reasons.
To effectively control the risks associated with working in a confined space, a Confined Space Hazard Assessment and Control Programme should be implemented for your workplace.
Before putting together this programme, make sure you review the specific regulations that apply to your workplace. All jurisdictions within Canada have regulations dealing with confined space entry. The regulations can vary slightly from jurisdiction to jurisdiction.
Identifying confined space hazards
Once a space has been identified as confined, the hazards that may be present within the confined space must be identified. Confined space hazards can be grouped into the following categories:
• Oxygen-deficient atmospheres
• Flammable atmospheres
• Toxic atmospheres
• Mechanical and physical hazards
Every confined space must be evaluated for these four types of hazards. The three types of atmospheric hazards are often the most difficult to identify since they might not be detected without the assistance of a gas monitor.
The following must also be done when using the alternate procedures:
• Ensure safety before removing a cover and guard opening immediately
• Test internal atmosphere (Oxygen, Flammables, Toxins) - observation available to entrant
• Continuous forced air ventilation
• Atmosphere periodically tested - observation available to entrant
• Evacuate immediately if necessary and evaluate what went wrong • Verify these procedures were conducted through a written certification
There must be documentation detailing that the space is safe for entry and the pre-entry measures were conducted. This ‘certification’ must contain the date, location of the space, and signature of the person making the verification. The certification must be made before entry and must be made available to all entrants or to their authorised representative(s).
Continuous forced air ventilation (FAV) must be used as follows:
• No entry until FAV has eliminated any hazardous atmosphere
• Direct FAV to ventilate immediate work area and areas where the entrant will likely be (be aware of pockets within the space)
• FAV must continue until all workers have left the space
• FAV must have clean source
• FAV must not increase the hazards in the space
The normal atmosphere is composed of approximately 21% oxygen and 79% nitrogen. An atmosphere containing less than 19.5% oxygen is considered oxygen-deficient. The oxygen level inside a confined space may be decreased as the result of either consumption or displacement.
Fire or explosions may occur in confined spaces which have
an atmosphere within the explosive limits of the gas (or liquid vapour). Explosive limits (also known as ‘flammable limits’), expressed in percentage, may be defined as the minimum and maximum concentrations of a flammable gas or vapour between which ignition can occur. Concentrations below the lower explosive limit (LEL) are too lean to burn while those above the upper explosive limit (UEL) are too rich.
Explosive/Flammable Limits Fire and explosion prevention
Work where a flame is used or a source of ignition may be produced (hot work) should not normally be performed in a confined space unless:
• All flammable gases, liquids and vapours are removed prior to the start of any hot work. Mechanical ventilation is usually used to:
1. Keep the concentration of any explosive or flammable hazardous substance less than 10% of its Lower Explosive Limit AND 2. Make sure that the oxygen content in the confined space is not enriched. Oxygen content should be less than 23% but maintained at levels greater than 18%. (These numbers can vary slightly from jurisdiction to jurisdiction)
• Surfaces coated with combustible material should be cleaned or shielded to prevent ignition
While doing the hot work, the concentrations of oxygen and combustible materials must be monitored to make certain that the oxygen levels remain in the proper range and the levels of the combustible materials do not get higher than 10% of the Lower Explosive Limit. In special cases it may not be possible, and additional precautions must be taken to ensure the safety of the worker prior to entering the confined space.
If a potential flammable atmosphere hazards are identified during the initial testing, the confined space should be cleaned or purged and ventilated, and tested again before entry to the confined space is allowed. Only after the air testing is within allowable limits should entry occur, as the gases used for purging can be extremely hazardous.
Toxic atmospheres may be present within a confined space as the result of one or more of the following:
1. The product stored in the confined space. When a product is stored in a confined space, the product can be absorbed by the walls and give off toxic vapours when removed or when cleaning the residual material. The product can also produce toxic vapours that will remain in the atmosphere due to poor ventilation. 2. The work being conducted in the confined space. Examples of such work include: welding or brazing with metals capable of producing toxic vapours, painting, scraping or sanding. Many of the solvents used for cleaning and/or degreasing produce highly toxic vapours. 3. Areas adjacent to the confined space. Toxic fumes produced by processes near the confined space may enter and accumulate in the confined space. For example, if the confined space is lower than the adjacent area and the toxic fume is heavier than air, the toxic fume may ‘settle’ into the confined space.
Air quality testing
The air within the confined space should be tested from outside of the confined space before entry. Care should be taken to ensure that air is tested throughout the confined space - side-to-side and top to bottom. A trained worker using detection equipment which has remote probes and sampling lines should do the air quality testing.
The sampling should show that:
• The oxygen content is within safe limits - not too little and not too much
• A hazardous atmosphere (toxic gases, flammable atmosphere) is not present
• Ventilation equipment is operating properly
The results of the tests for these hazards should be recorded on the Entry Permit along with the equipment or method(s) that were used in performing the tests.
Air testing may need to be ongoing depending on the nature of the potential hazards and the nature of the work. Conditions can change while workers are inside the confined space and sometimes a hazardous atmosphere is created by the work activities in the confined space.
How are hazards controlled in confined spaces?
The traditional hazard control methods found in regular worksites can be effective in a confined space. These include engineering controls, administrative controls and personal protective equipment. Engineering controls are designed to remove the hazard while administrative controls and personal protective equipment try to minimise the contact with the hazard.
However, often because of the nature of the confined space and depending on the hazard, special precautions not normally required in a regular worksite may also need to be taken. The engineering control commonly used in confined spaces is mechanical ventilation. The Entry Permit system is an example of an administrative control used in confined spaces. Personal protective equipment (respirators, gloves, ear plugs) is commonly used in confined spaces as well.
How is air quality maintained?
Natural ventilation (natural air currents) is usually not reliable and not sufficient to maintain the air quality. Mechanical ventilation (blowers, fans) is usually necessary.
• If mechanical ventilation is provided, there should be a warning system in place to immediately notify the worker in the event of a hazard or a failure in the ventilation equipment
• Care should be taken to make sure the air being provided by the ventilation system to the confined space is ‘clean’
• Ease of air movement throughout the confined space should be considered because of the danger of pockets of toxic gases still remaining even with the use of mechanical ventilation
• Do not substitute oxygen for fresh air. Increasing the oxygen content will significantly increase the risk of fire and explosion • The use of mechanical ventilation should be noted on the entry permit
Initially and during entry, test for: 1. Oxygen; 2. Flammables and 3. Toxins.
The individual conducting the air monitoring must be competent in the proper selection, use (placement, space stratification), maintenance, limitations (cross-sensitivity and chemical interference), and calibration. Be sure to read the manufacturer’s specifications.
Mechanical and physical hazards
Mechanical and physical hazards problems such as rotating or moving mechanical parts or energy sources can create hazards within a confined space. All rotating or moving equipment such as pumps, process lines or electrical sources within a confined space must be identified.
Energy sources controlled
All potentially hazardous energy sources must be de-energised and locked out prior to entry to the confined space so that equipment cannot be turned on accidentally.
Other safety precautions to be considered
Many other situations or hazards may be present in a confined space.
Be sure that all hazards are controlled, ensuring:
• Any liquids or free-flowing solids are removed from the confined space to eliminate the risk of drowning or suffocation
• All pipes should be physically disconnected or isolation blanks bolted in place. Closing valves is not sufficient
• A barrier is present to prevent and liquids or free-flowing solids from entering the confined space
• The opening for entry into and exit from the confined space must be large enough to allow the passage of a person using protective equipment
Hazardous Configuration is when the permit space has an internal configuration such that an entrant can be trapped or asphyxiated by inwardly converging walls, or by a floor that slopes downward and tapers to a smaller cross-section.
Common examples include hoppers and cyclones.
The best practice of controlling this hazard is eliminating the hazardous configuration by redesign or installing an effective, permanent barrier or guard to prevent a worker from falling and becoming trapped.
Personal fall protection would not eliminate a fall hazard but rather control the hazard.
Entering permit-required confined spaces
A written permit space programme must be established when spaces cannot be reclassified or alternative procedures cannot be used. This permit system simply ensures that all means, practices, and procedures necessary for safe permit space entry have been conducted.
The completed permit must be made available to the entrants or their authorised representatives by posting or other effective means.
The duration of the permit must not exceed the time required to?accomplish the identified task. The permit must be immediately cancelled when the entry operations have been completed or a condition not allowed under the entry permit arises in or around the permit space.
Cancelled permits must be retained for one year to assist in evaluating the permit space programme. Any problems during entry must be noted on the respective permit so this annual review can be effective.
The entry permit must document:
1. Permit space to be entered 2. Purpose of the entry 3. Date and duration of the entry permit 4. Authorised entrant(s) and attendant(s) 5. Entry supervisor and place for signature 6. Hazards of the permit space 7. Isolation measures - hazard controls (purging or ventilating) 8. The acceptable entry conditions 9. Test results (initial/periodic) with initials/name of tester and time 10. Rescue/emergency services available and means to summon 11. Communication procedures between entrant and attendant 12. All necessary equipment (PPE, testing or communication equipment) 13. Other necessary information and/or additional permits (hot work, for example)
Written permit space programme
The intent of this permit space programme is to manage and evaluate your permit space entries. The items on the permit address the components of your written plan to ensure safety and health of all involved. Your written plan must include:
• The measures implemented to prevent unauthorised entry
• The identification and evaluation of all permit space hazards prior to entry
• The development and implementation of safe entry operations
• Providing and maintaining all necessary equipment (such as PPE or monitors)
• Evaluating permit space conditions before and during entry operations
• Providing at least one attendant and developing procedures for multiple spaces
• Designating and training all persons who have active roles
• Developing and implementing rescue and emergency procedures
• Developing and implementing the entry permit procedures
• Coordinating multi-employer entry procedures
• Developing procedures for concluding the entry (closing off the space)
• The review and evaluation of entry operations during the year (as needed)
• The annual permit space programme review using the historic permits
The entry team and their roles
The Entry Supervisor:
• Knows the hazard(s), symptoms and consequences
• Verifies the permit by determining if acceptable entry conditions exist
• Authorises entry
• Oversees entry operations
• Terminates entry
• Verifies rescue services
• Removes unauthorised individuals
• Serves as attendant, if necessary
• Knows the hazard(s), symptoms, and consequences
• Aware of potential behavioural effects
• Monitors entrants and maintains count
• Monitors hazards and activities in and outside of the permit space
• Remains outside entry point
• Communicates with entrant(s)
• Controls entry point
• Summons rescuers
• Initiates/performs non-entry rescue if required
• Knows the hazard(s), symptoms, and consequences
• Uses equipment properly
• Communicates regularly with the attendant
• If the unexpected occurs, alerts the attendant
• Exits immediately if hazard(s) develops
Rescue and emergency services
There are three options to permit-required confined space rescue.
1. Arrange for rescue service from an outside source. Evaluate their ability to respond in a timely manner considering the hazard(s) evaluated and proficiency with rescue-related tasks and equipment. ‘Timely’ will vary according to the specific hazards involved.
Provide the rescue service with access to all permit spaces from which rescue may be necessary so they can develop appropriate rescue plans and practice rescue operations. 2. Arrange for your own employees to provide rescue.
Provide necessary PPE and training in the PPE: that is, training in their assigned rescue duties, training in first aid and CPR, practice simulated permit space rescues at least annually in respective spaces using manikins or actual persons. 3. Provide for non-entry rescue. Provide necessary retrieval equipment such as a full body harness and a mechanical device when permit space depths are more than five feet.
If a chemical is involved during an emergency, provide the necessary MSDS (Material Safety Data Sheets) immediately.
Appropriate training is extremely important to working safely in confined spaces. Hands-on training should be an essential part of the confined space training.
Every worker that enters a confined space must be fully trained on:
• Recognition and identification of potential hazards associated with the confined spaces that will be entered
• Evaluation and control procedures for the identified or potential hazards
• All equipment such as ventilation equipment (blowers), harnesses and air quality monitors (e.g. oxygen/combustible meters) that will be used while in the confined space
• All personal protective equipment (e.g. respirators) that the worker will be using while in the confined space
• All procedures for entering the confined space as outlined in the employer’s Confined Space Hazard Assessment Programme
• Procedures to follow in the event of a situation developing that could present additional risk to the worker or an emergency
• The specific work to be done while in the confined space
Workers with emergency rescue responsibilities will need additional specialised training. All confined space training should include some hands-on training with the safety equipment including the personal protective equipment and safety harnesses. Rescue procedures should be practiced frequently so there is a high level of proficiency. Employers should keep records of all confined space training including refresher courses.
Personal Protective Equipment
Personal protective equipment (PPE) includes all types of equipment used to increase individual safety while performing potentially hazardous tasks. This may include safety glasses, hard hats, gloves, lab coats, respirators, or any equipment used to protect against injury or illness.
The Health and Safety law in most countries requires PPE to be provided for employees, used, and maintained in a sanitary and reliable condition wherever hazards of processes or environment, chemical hazards, radiological hazards, or mechanical irritants are encountered in a manner capable of causing injury or illness through absorption, inhalation, or physical contact. Employers are responsible for ensuring the adequacy of the equipment and ensuring that it is properly maintained, even in those cases where employees provide their own PPE.
Engineering controls that eliminate the hazard at the source and do not rely on the worker’s behaviour for their effectiveness offer the best and most reliable means of protection. Therefore, engineering controls are the first choice for eliminating workplace hazards. Whenever engineering controls are not available or are not fully capable of providing protection, the worker must wear personal protective equipment.
Departments must assess their workplaces to identify hazards requiring the use of PPE. Equipment should be selected to provide protection against the hazards identified during the assessment. The hazard assessment must be certified in writing.
Respiratory protection may be used to protect against inhalation hazards when engineering and administrative controls are not feasible or adequate.
Each worker required to use PPE must receive training in the following:
• How to properly wear PPE
• What types of PPE provide protection against the hazards identified during the assessment
• When PPE must be used
• The proper care and useful life of PPE
• Proper disposal of damaged PPE ?
Saeed Taki MSc, CEng, MlMechE, FIOSH, RSP. Training leader of the Safety Training Center, Bahrain, specialising in risk assessment, risk investigation and safety technology. He has more than 15 years of managerial experience in big and prominent industrial companies. He has credible expertise in System Safety and Probabilistic Risk Assessment (PRA) applications and methodology development. He has led and performed safety and risk analysis on many projects. He is currently consultant of Safety and Health in STC-Bahrain. He is responsible for system safety HSMS and requirements as well as OHSAS 18001 and 18002. He is also a consultant and auditor for health and safety management systems. www.osedirectory.com/health-and-safety.php
Published: 10th Nov 2010 in Health and Safety Middle East