Search First Intervention Team

by Luke Hayes on 2nd July 2023

Key Points:

  • Confined space risk assessments are vital to keeping workers safe
  • Confined spaces present risks that aren’t found elsewhere and require careful consideration to reduce or remove their impact
  • There are different confined space risk levels, with higher risk environments requiring more detailed risk assessments.
  • The key dangers faced by workers in confined spaces
  • The things you can do to reduce the risk workers face in confined spaces

What Is a Confined Space Risk Assessment?

A confined space risk assessment is a systematic process of identifying, evaluating, and controlling the hazards associated with working in confined spaces. Confined spaces, such as tunnels, silos, vats, or other enclosed structures, can pose significant risks to workers due to their limited access and egress, poor ventilation, or potential for hazardous substances or conditions.

The risk assessment process involves identifying potential hazards, such as toxic gases, lack of oxygen, extreme temperatures, or the risk of engulfment. Once these hazards are identified, they are evaluated based on their potential impact and likelihood of occurrence.
Control measures are then put in place to mitigate these risks, which may include the use of personal protective equipment (PPE), ventilation systems, or rescue plans. Regular reviews of the risk assessment are crucial to ensure the ongoing safety of workers in these environments.


What Makes a Confined Space?

There are three main signs that you’re working in a confined space and these are all simple and easy to spot without training.

The area has limited openings for entry and exit

An area with limited openings for entry and exit is one of the defining characteristics of a confined space. This feature significantly impacts the accessibility and safety of the space.

Limited openings can make it difficult for workers to enter or exit quickly, especially in emergency situations. This can lead to an increased risk of injury or fatality in the event of a sudden hazard, such as the release of toxic gases, a fire, or a structural collapse.

Additionally, these restricted access points can also hinder rescue operations, as rescuers may struggle to reach individuals trapped inside. Furthermore, limited openings can contribute to poor ventilation, leading to the build-up of hazardous substances or a deficiency of oxygen.


The area is just enough for a worker to enter and conduct work

An area that is just large enough for a worker to enter and conduct work is another characteristic of a confined space. This attribute often implies that the space is not designed for continuous occupancy, which can present a variety of challenges and hazards.

The limited space can restrict movement and limit the worker’s ability to react quickly or effectively in case of an emergency. It can also contribute to physical discomfort or strain over time, potentially leading to decreased alertness or efficiency.

Furthermore, the confined nature of the space can exacerbate the effects of any hazardous substances or conditions present, as there is less room for these to disperse than in a more open environment. For example, harmful gases or heat can build up more quickly, increasing the risk to the worker.


The area is not intended for continuous human occupancy

An area not intended for continuous human occupancy is the final characteristic that defines a confined space. This means that the space is not designed with the necessary features and safeguards to support workers for extended periods.

Such spaces may lack adequate ventilation, lighting, or temperature control, making them unsuitable for prolonged work. The absence of these features can lead to the accumulation of hazardous gases, poor visibility, or extreme temperatures, all of which can pose serious risks to workers. Furthermore, because these spaces are not designed for humans to work in for long periods, they often lack the necessary facilities for comfort and well-being, such as rest areas or toilet facilities. This can lead to physical and mental strain over time, further increasing the risk of accidents or health issues.


What Are the Types of Confined Spaces?

There are many different kinds of confined spaces and we have provided some examples of common confined spaces that workers may find themselves in, depending on their job role and industry. Confined spaces generally fall into three categories, low-risk confined spaces, medium-risk confined spaces and high-risk confined spaces. These can also be broken down into National Classification levels 1,2,3 and 4.
The higher the national classification level the more in-depth your confined space risk assessment needs to be.


NC1 Low-risk confined space

NC1 confined spaces are low-risk confined spaces and they have shallow entry and adequate mechanical or natural ventilation. Access is simple and without any obstructions and the risk of flooding is very low. NC1 confined spaces include meter pits, valve chambers and PRV chambers. These areas do not require breathing apparatus unless required for the nature of the work being carried out.


NC2 Medium risk confined space

A confined space is considered a medium risk when there are challenges related to entering or exiting the space. In these situations, there’s a reasonable chance that a specific hazard may be present. Additionally, certain risks could be introduced during the course of the work being performed. In essence, a medium-risk confined space is one where access is not straightforward, specific hazards are likely to be encountered, and the nature of the work could potentially introduce new risks.

An NC2 medium-risk confined space is where the worker has direct, vertical access and is continuously attached to a man-riding winch or similar rescue device.


NC3 Medium risk confined space

The NC3 classification is given to a medium-risk confined space where it is not possible for the worker to be continuously attached to a man-riding winch or similar device. Usually, there will be a team of workers who move away from an exit point. For example, entering a sewer system through a manhole and then navigating through the tunnels.


NC4 High-risk confined space

A high-risk confined space is defined as a space that has complex entry or exit points, or where serious hazards are present or likely to develop.

The NC4 classification is given to confined spaces that involve non-standard entries and complex operations which add additional risk to workers. These additional risks require specific controls as well as rescue arrangements.


Examples of Confined Spaces and Associated Hazards

Tanks and Vessels: These are enclosed containers often used for storing liquids, gases, or bulk materials. They can pose risks due to the potential presence of hazardous substances, lack of oxygen, or the risk of engulfment.

Silos and Storage Bins: These are tall, tower-like structures used for storing bulk materials like grain or coal. They can pose similar risks to tanks and vessels, with the added risk of materials collapsing or flowing, potentially trapping a worker.

Pits and Trenches: These are excavated areas that are deeper than they are wide. They can pose risks due to their depth, the potential for collapse, and the potential presence of hazardous gases.

Manholes and Tunnels: These are often found in utility and construction work and can pose risks due to their depth, limited access and egress, and potential for hazardous conditions, such as the presence of gases or the risk of flooding.

Pipelines and Ductwork: These are enclosed paths for transporting substances such as water, gas, or air. They can pose risks due to their narrow and elongated nature, potential for hazardous substances, and lack of oxygen.

Vaults and Chambers: These are enclosed spaces that may house equipment or be used for storage. They can pose risks due to their limited access and egress, potential for hazardous conditions, and lack of ventilation.


What Are the Main Dangers in a Confined Space?

Confined spaces can present a variety of hazards, some of which can be life-threatening. Here are some of the main dangers associated with confined spaces:

  • Toxic Atmosphere: The presence of harmful gases, vapours, or fumes can lead to poisoning or asphyxiation. This can be due to the work being performed, the materials stored in the space, or natural processes.
  • Oxygen Deficiency or Enrichment: A lack of oxygen can cause unconsciousness or death. On the other hand, an oxygen-enriched atmosphere can increase the risk of fires or explosions.
  • Flammable or Explosive Atmospheres: Certain gases, vapours, or dust can ignite or explode, causing severe injuries or death.
  • Engulfment: Loose materials, such as grain, sand, or other bulk substances, can engulf and suffocate a worker.
  • Physical Hazards: These can include extreme temperatures, noise, radiation, or the presence of hazardous substances. The design of the space itself can also pose risks, such as tight spaces that can trap a worker or sharp objects that can cause injuries.
  • Poor Visibility: Limited light can hide hazards and make tasks more difficult, increasing the risk of accidents.
  • Difficulty in Access and Egress: Limited or difficult access can make it hard to escape quickly in an emergency and can hinder rescue efforts. This is why we recommend that all workers entering a confined space wear a harness which makes rescue much quicker.
  • Drowning or Asphyxiation: In some confined spaces, there’s a risk of flooding or the presence of liquids or free-flowing solids that can lead to drowning or asphyxiation.
  • Each of these hazards requires specific control measures to ensure the safety of workers entering or working in confined spaces. These control measures should be clearly defined within your risk assessment and we’ll explore some in the next section.


How Can You Reduce the Risks Associated With Working in a Confined Space?

There are many ways you can rescue the risks associated with working in confined spaces. These include the basics we’re used to outside of confined spaces such as PPE, safe systems of work and training however these will need to be toiled to the confined space being worked in.


Safe System of Work

A safe system of work (SSOW) is a formal procedure that results from a systematic examination of a task in order to identify all the hazards. It defines safe methods to ensure that hazards are eliminated or risks are reduced to acceptable levels. This system includes the procedures, people, equipment, and materials that contribute to the execution of a task. These include procedures for entering and exiting the space, communication methods, use of tools and equipment, and emergency response.



Personal Protective Equipment (PPE) plays a crucial role in reducing the risks associated with working in confined spaces. When working in confined spaces we recommend the following PPE is always used but always carry out a risk assessment as every situation differs.

  • Respiratory Protection: Confined spaces often have poor ventilation and can contain toxic gases or lack sufficient oxygen.
  • Protective Clothing: Depending on the hazards present, workers may need to wear protective clothing. This could include chemical-resistant suits to protect against hazardous substances, heat-resistant clothing for high-temperature environments, or full-body suits to protect against engulfment in loose materials.
  • Safety Harnesses and Lifelines: In the event of an emergency, a worker may need to be quickly retrieved from a confined space.
  • Eye and Face Protection: Goggles, face shields, or full-face respirators can protect against splashes of hazardous substances, dust, or flying debris.
  • Head Protection: Hard hats can protect against falling objects or bumps against overhead structures.
  • Hearing Protection: In noisy environments, earplugs or earmuffs can protect against hearing damage.
  • Gloves and Footwear: Depending on the work being done, workers may need gloves to protect against cuts, burns, or exposure to harmful substances, and safety boots to protect against falling objects or punctures.

Remember, PPE is the last line of defence and should be used in conjunction with the other safety measures listed. Training on correctly using and maintaining PPE is also essential to ensure its effectiveness.



Ventilation plays a critical role in maintaining a safe environment within confined spaces. It can help reduce risks by:

  • Removal of Hazardous Substances
  • Improving Oxygen Supply
  • Temperature Control
  • Prevention/reduction of Flammable Atmospheres

It’s important to note that the effectiveness of ventilation in reducing risks in confined spaces depends on several factors, including the design of the space, the nature of the work being done, and the type of ventilation system used. In some cases, natural ventilation may be sufficient, while in others, mechanical ventilation systems may be required. Regular monitoring of air quality is also crucial to ensure that ventilation is effective and that conditions within the confined space remain safe.


Cleaning and removal of residues

Cleaning and removing residues in confined spaces can significantly reduce the risks associated with working in these environments. Here’s how:

  • Elimination of Hazardous Substances: Many confined spaces, such as tanks or silos, may have residues from substances that were previously stored or used in them.
  • Prevention of Engulfment: In spaces that store loose materials, residues can pose a risk of engulfment. Cleaning can help reduce this risk.
  • Improved Visibility and Access: Residues can obscure visibility and make surfaces slippery, increasing the risk of accidents.
  • Prevention of Biological Hazards: In some confined spaces, residues can promote the growth of harmful bacteria or fungi, or attract pests.
  • Improved Air Quality: Some residues can produce dust or vapours that can reduce air quality and potentially lead to respiratory problems.

It’s important to note that cleaning confined spaces often involves its own set of hazards and may require confined space access to perform the cleaning required. The risks of cleaning need to be taken into account and may not be beneficial if they introduce more risk.


Fire prevention

Just like when working in regular spaces, fire prevention is key to keeping workers safe. However, fires in such confined spaces can be particularly dangerous due to limited exits, the potential for rapid spread, and difficulty in fighting the fire. Some fire prevention methods to think about include:

  • Elimination of Ignition Sources
  • Control of Flammable Substances
  • Safe Work Practices: Using non-sparking tools, prohibiting smoking, and controlling static electricity can help prevent fires. Hot work, such as welding or cutting, should be avoided if possible, or done under strict controls if necessary.
  • Fire Detection and Suppression Equipment

By implementing these fire prevention measures, the risk of a fire occurring in a confined space can be significantly reduced, making the environment safer for workers.


Permit-to-work systems

A permit-to-work system is a formal written system used to control certain types of work that are potentially hazardous. Implementing a permit-to-work system for confined spaces can significantly reduce risks by ensuring that all safety precautions are taken and only trained personnel are entering these spaces.


Atmospheric testing and monitoring

Atmospheric testing and monitoring are critical safety measures for working in confined spaces. Testing and ongoing monitoring can significantly reduce risks associated with toxic gasses, flammable vapours and a lack of oxygen.

It can also be used to verify the effectiveness of other risk reduction methods such as verifying if ventilation is reducing the concentration of hazardous gas or proving enough oxygen. Another benefit of continuous testing is that if the worst should happen and a rescue team is required to safely evacuate a casualty from a confined space they are aware of the conditions inside.

By providing real-time information about the conditions within the confined space, atmospheric testing and monitoring can help prevent exposure to hazardous conditions, inform the selection and implementation of safety measures, and guide emergency response efforts.


Emergency arrangements & Protocols

While no one expects an emergency, especially in routine jobs, if things do go wrong having a clear plan with your emergency protocols and arrangements will reduce the risk of casualties and the risk of the rescue team entering the confined space.

  • Emergency protocols should include plans for evacuation, rescue, first aid, and communication with emergency services.
  • Training and emergency drills ensure that everyone is familiar with the emergency procedures and quickly and calmly responds to the emergency.
  • Rescue equipment and rescue teams, where required, should always be on standby during any confined works. The difference between having rescue equipment ready to operate and having to source it can be the difference between a close call or someone becoming severely injured or even losing a life.
  • Effective communication is crucial in an emergency. Emergency protocols should include a system for alerting workers in a confined space of an emergency, as well as for communicating with rescuers and emergency services.
  • Emergency protocols should designate roles for different workers, such as who will call for help, who will provide first aid, and who will attempt a rescue.
  • After an emergency, protocols should include procedures for reporting the incident, investigating what happened, and implementing measures to prevent a recurrence.



Training plays a vital role in reducing the risks associated with working in confined spaces. Here’s how:

  • Awareness of Hazards in confined spaces
  • Safe Work Practices when operating in confined spaces
  • Use and maintenance of Personal Protective Equipment (PPE):
  • Emergency Procedures if something goes wrong
  • Correct Use of Safety Equipment:
  • Communication in emergency situations

By equipping workers with the knowledge and skills they need to work safely in confined spaces, training can significantly reduce the risk of accidents and injuries.


Final Thoughts

In conclusion, conducting thorough and effective confined space risk assessments is essential for ensuring the safety of workers in these potentially hazardous environments. By identifying and evaluating the risks associated with confined spaces, implementing appropriate control measures, and providing comprehensive training, organizations can significantly reduce the likelihood of accidents, injuries, and health issues.

From safe systems of work to personal protective equipment, ventilation, emergency protocols, and ongoing monitoring, every aspect of the risk assessment process plays a crucial role in safeguarding workers and promoting a culture of safety. By prioritizing and investing in confined space risk assessments, we can create work environments that prioritize the well-being of every individual, enabling them to carry out their tasks with confidence and peace of mind.

If you need support with creating your confined space risk assessments or would like peace of mind by having an expert check your risk assessment then contact the rescue experts at FIT. We also provide rope and standby rescue teams so once your works commence you have an experienced team ready to step in during an emergency.


FAQs About Confined Space Risk Assessment

What is a confined space risk assessment?

A confined space risk assessment is a systematic process of identifying, evaluating, and controlling the hazards associated with working in confined spaces. It involves identifying potential hazards, assessing their likelihood and potential impact, and implementing control measures to mitigate these risks.


Why is a risk assessment important for working in confined spaces?

A risk assessment is crucial as it helps to identify potential hazards in a confined space, evaluate the level of risk, and determine appropriate control measures. This process helps to prevent accidents, injuries, and health issues, ensuring the safety of workers.


Who is responsible for conducting a confined space risk assessment?

Typically, the employer or a designated safety officer is responsible for conducting a confined space risk assessment. In some cases, an external consultant or specialist may be hired to perform the assessment.


What are the key elements of a confined space risk assessment?

Key elements include hazard identification, risk evaluation, implementation of control measures, documentation of the findings, and regular review and update of the risk assessment.


How often should a confined space risk assessment be conducted?

A risk assessment should be conducted before any work begins in a confined space. It should also be reviewed and updated regularly, or whenever there are changes in the work activity, the confined space, or after an incident.


What are the common hazards identified in a confined space risk assessment?

Common hazards can include toxic gases, lack of oxygen, extreme temperatures, risk of fire or explosion, risk of engulfment, and difficulty in access or egress.


How can the risks identified in a confined space risk assessment be mitigated?

Risks can be mitigated through various control measures such as the use of personal protective equipment (PPE), implementation of safe work procedures, use of ventilation systems, atmospheric testing and monitoring, and emergency planning.


What is the role of personal protective equipment (PPE) in a confined space risk assessment?

PPE is a key control measure in protecting workers from identified hazards. The risk assessment will determine what PPE is necessary, such as respirators, protective clothing, or safety harnesses.


How does a permit-to-work system relate to a confined space risk assessment?

A permit-to-work system is a formal procedure that ensures all risks have been assessed and controlled before work begins in a confined space. It’s an important part of implementing the findings of a risk assessment.


What training is necessary for workers involved in a confined space risk assessment?

Workers should be trained in hazard identification, risk assessment procedures, safe work practices, use of PPE, emergency procedures, and the specific hazards and controls related to their confined space work.


What are the emergency procedures in a confined space risk assessment?

Emergency procedures are plans for responding to emergencies in confined spaces, such as a fire, toxic gas release, or a worker becoming incapacitated. They include evacuation procedures, rescue plans, and first aid procedures.


How does atmospheric testing fit into a confined space risk assessment?

Atmospheric testing is used to identify and evaluate hazards such as toxic gases or lack of oxygen. It’s a crucial part of the risk assessment and helps to determine necessary control measures and emergency procedures.


What is the role of ventilation in a confined space risk assessment?

Ventilation can be used as a control measure to reduce risks such as toxic gases or lack of oxygen. The risk assessment will determine whether ventilation is necessary and what type of ventilation system should be used.


How are the results of a confined space risk assessment communicated to workers?

The results should be communicated to all workers involved in the confined space work. This can be done through safety meetings, training sessions, or written communications such as safety bulletins or signage. Workers should be informed of the hazards identified, the control measures in place, and the emergency procedures.


What should be done if the risks identified in a confined space risk assessment cannot be adequately controlled?

If risks cannot be adequately controlled, work should not proceed in the confined space until further control measures can be implemented or the hazards can be eliminated. This could involve changing the work process, using different equipment, or in some cases, redesigning the confined space.


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