In this article, we will consider what constitutes a confined space, what hazards and risks exist through confined space entry, and what precautions and actions we can take to eliminate or minimise those risks.

First, we must understand what constitutes a “confined space”.

There are a number of characteristics that we can consider.

A confined space is typically a place that was not designed and constructed for normal/regular human work activity. It has limited openings for entry and exit (sometimes referred to in literature as access and egress) and will generally have poor and sometimes no natural ventilation. This lack of ventilation forms one of the key hazards with entry into confined spaces as we will see shortly.

Entry Into Confined Spaces

We probably all have an impression of examples of confined spaces like: boilers, pressure vessels, cargo holds, cargo tanks, ballast tanks, sewage-tanks, pump-rooms, compressor rooms, wells, shafts, tunnels and pipelines. However, confined spaces can also include more spurious examples, they are not always “rooms” and sometimes have limited boundaries. To illustrate this point I wanted to highlight two investigations which I was personally involved in.

The first involved a technician working on the forecourt of a petrol station (gas station). He was lying on the ground and had opened up a small metal plate (30cm2) to work on a fuel valve that was perhaps 20cm below ground level. The opening was just large enough for him to get his hands and part of his head into the space. At the time, I do not think anyone even considered the idea that this might represent a confined space. However, unfortunately, the heavy fuel fumes in the small underground space had displaced all the breathing air and the technician asphyxiated. 

“confined spaces are not always obvious and we have to ensure that associated risk assessment considers confined space”

The second case was perhaps more classic, but again, might not always strike people as being confined. In this case a welder was working on a very large diameter pipe (1.5m). It was fully open behind him and the welding area was no more than 1 metre from the opening. Again, I think that the large opening convinced everyone involved that this could not be a confined space, but once again, the breathing air was displaced, in this case through the work activity, and the welder was asphyxiated.

Therefore, the key message here is that confined spaces are not always obvious, and we have to look very carefully at the work activity and ensure that associated risk assessment considers confined space hazards where there may be poor or limited natural ventilation.

The risks of working in confined spaces  

  • An atmosphere that does not have a safe oxygen level
  • Fire or explosion from the ignition of flammable contaminants
  • Difficulty rescuing and treating an injured or unconscious person
  • Asphyxiation resulting from oxygen deficiency or immersion in free-flowing materials such as liquids, grain, sand, or fertiliser
  • Loss of consciousness, injury or death due to the immediate effects of airborne contaminants (including airborne gases, vapours and dusts that may cause injury from fire or explosion)

Entry and exit

Entry into a confined space means any situation in which any part of the body of any person is located within the space regardless of the length of time taken. This can also take into consideration the depth of exposure versus the height of the worker where there is direct or indirect exposure to an unknown substance, such as a contaminated gas, which may affect the health of a worker. This is particularly relevant in cases where the person is working in a trench, where their head may ordinarily be above the trench line, but if they bend down to work, suddenly their breathing zone is now in the trench and if there are gases or fumes present that are heavier than air, then they may displace all the breathable air. Remember, you do not need a total lack of oxygen to create a hazard, a short reduction from 21% to 16%, even for just few seconds, may be insufficient to support life.

Entry Into Confined Spaces

The first question we must always ask is can we eliminate the need to enter the confined space? The advance of new technologies is now helping us in this capacity: we can use drones to conduct inspections inside tanks, and we can use robots to weld inside pipelines and to clean inside tanks. However, there will be cases when we cannot avoid entering a confined space, and therefore, we must carefully consider what precautions we can take to minimise the risk to our employees and contractors.

Risk assessment

We must be specific and systematic in our approach to the management and control of risks associated with entry into confined spaces.

  • Identifying hazards associated with confined spaces
  • Assessing the risks associated with these hazards
  • Implementing risk control measures
  • Reviewing risk control measures
  • Identifying risk mitigation measures
  • Confirm a detailed rescue and recovery plan

The risk assessment must cover the full scope of works planned, plus any potential rescue operation. While planning any rescue operation, thought must be given to the location of the entry (i.e. remote location) and the time for any emergency assistance to arrive.

The risk assessment must also identify other precautions required due to the type of space, its layout, the surrounding environment and any other factors. Identifying these factors is important, as other permits, training requirements or equipment may be required prior to entry and will vary from site to site. Examples of other factors may include:

  • Fall from heights requirements
  • Hot works or chemical usage
  • Potential ignition (such as lighting or electrical tools)
  • Contaminant sources
  • Atmospheric conditions

If at any time during the work activity the conditions change, then the team should “stop work” and reassess hazards to ensure the risk assessment is still valid. If it is not then it should be formally modified and documented.

The risk assessment must be available prior to, during, and after completion of any or all entries and work in the confined space.

Entry Into Confined Spaces

Generic risk assessments may be used for repeated tasks or entries into similar spaces. It is the responsibility of the person in charge performing the entry to show that the risk assessment is relevant to the space being entered.

A risk assessment is a documented assessment of all hazards associated with the work, the risk levels, and the controls required to ensure work can be performed safely. When undertaking a risk assessment to determine the risks requiring control, the assessment will need to consider the following in most cases:

  • The hazards identified
  • The task
  • The working environment
  • Work materials and tools
  • All permits associated with the work
  • The additional physiological and psychological demands of the task
  • Arrangements for emergency rescue
  • Training requirements

Safe oxygen level

An atmosphere containing not less than 19.5% and not more than 23.5% oxygen.

Person in charge of the entry

The person responsible for the overall supervision of the work being conducted within the confined space.


A person who has the responsibility of assisting the person/s entering or exiting the confined space must complete the work permits to ensure all persons and equipment have exited the confined space, and instigate emergency response from outside the confined space.

Standby personnel

Personnel within the immediate vicinity (sight and sound) who will make initial contact with emergency services if required, and provide initial emergency rescue response from outside the confined space.

Gas detectors

Standard electronic gas detection meters must be approved and be capable of testing.

Atmospheric testing

Pre-entry testing must occur before every entry into the confined space. Results must be recorded on the associated Permit to Work.

Pre-entry testing must be conducted for oxygen, carbon monoxide, hydrogen sulphide and explosive-gas levels.

The measurement of atmospheric, explosive and relevant hazardous gas concentration levels, must be undertaken and interpreted by appropriately trained persons.

Entry Into Confined Spaces

If pre-entry testing shows non-compliance with any of the required levels, the space must not be entered.  Appropriate options to improve the atmospheric conditions must be implemented and compliance with acceptable entry limits must be achieved before entry is permitted.

If explosive gases are found to be present at concentrations greater than 5% of their LEL after 10 minutes, all opened entries should be closed and the job location reported to the relevant supervisor immediately. Continuous monitoring is required for all confined space entries.

If the entry party is required to exit the space as a result of the gas detector alarming, the space must be reassessed prior to any re-entry to ensure conditions are returned to acceptable levels.

Other contaminants

In some confined spaces it will be necessary to monitor for atmospheric contaminants in addition to those listed above.

This may be because the atmosphere may be affected by:

  • Non-compliant industrial discharges, particularly sewerage assets
  • Tasks being performed by other persons around the space
  • Observation of abnormal conditions by the work crew
  • Spillages or discharges into drains
  • The task performed requiring the use of materials containing volatile solvents

This last bullet is particularly relevant to cases where tank cleaning is taking place. Gas detection and atmospheric readings prior to entry may indicate a safe breathing environment, however, once the cleaning starts and the sludge is disturbed, vapours contained in the sludge will be released into the confined space. In many cases these vapours are heavier than air and will start to displace air out of the tank, and may then create a hazardous atmosphere for the people working in the tank. This is an example where forced ventilation and continuous atmospheric monitoring would be required.

“rescuers need to be properly trained and protected against the cause of the emergency”

Therefore careful consideration must be given to the following:

1.  The location of the confined space – the geographic location of the space, its accessibility in an emergency and the distance to appropriate medical facilities all need to be taken into account.

2.  Communications – How can people working inside the space communicate to people outside in an emergency? Exactly how will the alarm be raised and by whom? Planning needs to ensure that rescue and emergency personnel can access the workplace during night shifts, weekends and holiday periods.

3.  Rescue and resuscitation equipment – the provision of suitable rescue and resuscitation equipment will depend on the potential emergencies identified. Training in the correct operation of rescue equipment is essential where such equipment is provided. Selected rescue equipment needs to be in close proximity to the confined space and able to be used immediately.

4.  Capabilities of rescuers – rescuers need to be properly trained, sufficiently fit to carry out their task and capable of using any equipment provided for rescue (e.g. breathing apparatus, lifelines and fire-fighting equipment). Rescuers also need to be protected against the cause of the emergency.

5.  First aid procedures – trained first aiders need to be available to make proper use of any necessary first aid equipment provided.

6.  Local emergency services – if local emergency services are to be relied upon for rescue.


Radio or telephone communication must be available at all times onsite to enable contact with the relevant control room and/or emergency services.

Continuous communication must be maintained between those inside and outside the space.

Ideally voice communication will be available, but other forms of communication may also be considered in combination: Visual (hand signals), torch signals, whistles, horns and CCTV.

The method of communication must be documented in the risk assessment prior to entry.

Personal Protective Equipment

Wear protective headwear as required when working in confined spaces. This is for protection from objects being lowered or accidentally dropped from above. Bump caps may be worn in areas such as smaller diameter sewers, drains or pipes, if there is no risk of objects falling from above. No equipment is to be raised or lowered directly above persons wearing bump caps.

The selection of the appropriate protective clothing to be worn within a confined space depends both upon the type of confined space and the work being performed.

The risk assessment prepared for the work being performed must identify the specific protective clothing requirements for the task.

Use of safety lines

Where safety lines are attached to the person entering the confined space, then a dedicated “standby person” should control the safety line at all times. If the need to disconnect from the safety line occurs while within the confined space, the risk assessment must be revised to take into account the potential for different hazards and different types of rescue that may be required.