Confined Spaces FAQs

A confined space is an enclosed or largely enclosed area with restricted entry or exit, where the environment can become dangerous due to hazards such as toxic gases, low oxygen, or the risk of fire, flooding, or entrapment.

There is no fixed types of confined space in UK guidance. Instead, a space is defined as a confined space if it is enclosed or largely enclosed and presents a risk of serious injury from hazardous conditions.

Common examples include tanks, pits, silos, ducts, sewers, cellars, and chambers.

Under the Confined Spaces Regulations 1997, a space is classed as a confined space if it presents one or more of the following five specified risks:

1. Serious injury from fire or explosion
2. Loss of consciousness arising from an increase in body temperature
3. Loss of consciousness or asphyxiation due to gas, fume, vapour, or lack of oxygen
4. Drowning from an increase in the level of a liquid
5. Asphyxiation due to a free-flowing solid (such as grain or powder)

The most dangerous hazard in confined spaces is a lack of oxygen or the presence of toxic gases, as these can cause collapse, unconsciousness, or death within seconds and often without warning.

Methane gas is dangerous in confined spaces because it can displace oxygen, causing suffocation, and it is highly flammable and explosive when mixed with air. Even small accumulations can ignite and lead to fires or explosions if an ignition source is present.

A trench can be a confined space, but not always. It becomes a confined space when it is enclosed enough and poses serious risks such as low oxygen, toxic gases, or the potential for flooding, engulfment, or collapse.

Yes. An open excavation can become a confined space if conditions create serious risks such as a build-up of gases, low oxygen levels, flooding, or the potential for entrapment or engulfment. Even without a roof, hazardous atmospheres or restricted movement can make it a confined space.

A cofferdam can be a confined space if it is enclosed enough and presents risks such as low oxygen, toxic gases, flooding, or entrapment. Whether it is a confined space depends on the specific conditions rather than the structure itself.

A culvert is often a confined space because it is enclosed, has limited access, and can contain hazards such as low oxygen, toxic gases, water flow, or the risk of entrapment. Whether it qualifies formally depends on the specific conditions and risks present.

A lift shaft can be a confined space, but it depends on the risks present. If the shaft is enclosed and there is a danger such as low oxygen, hazardous fumes, entrapment, or difficulty entering or exiting, it meets the definition of a confined space under UK regulations.

A loft is not usually a confined space, but it can become one if it is enclosed enough and contains serious risks such as low oxygen, hazardous fumes, poor ventilation, or restricted access. Its status depends on the specific conditions and hazards present.

A manhole is often a confined space because it is enclosed, has restricted access, and can contain hazards such as toxic gases, low oxygen, or the risk of flooding or entrapment. Its classification depends on the specific conditions and risks present.

A pit can be a confined space. If it is enclosed or largely enclosed and presents risks such as low oxygen, toxic gases, entrapment, or engulfment, it meets the definition of a confined space under UK regulations.

A roof space is not usually a confined space, but it can become one if it is enclosed enough and contains serious risks such as poor ventilation, low oxygen, heat build-up, or restricted access. Its classification depends on the specific hazards present.

A shipping container can be a confined space. Although it is not always treated as one, it becomes a confined space if it is enclosed and presents serious risks such as low oxygen, hazardous fumes, heat build-up, or restricted entry and exit.

A silo is often a confined space because it is enclosed, has restricted access, and can contain serious hazards such as low oxygen, toxic gases, dust buildup, or the risk of engulfment. Its classification depends on the specific conditions and risks present.

A suspended floor can be a confined space if it is enclosed enough and presents serious risks such as poor ventilation, low oxygen, hazardous fumes, or restricted access. Its classification depends on the specific conditions and hazards present.

A tunnel is often a confined space because it is enclosed, has limited access, and can contain hazards such as low oxygen, toxic gases, water ingress, or the risk of entrapment. Whether it is treated as a confined space depends on the specific conditions and risks present.

A vehicle inspection pit can be a confined space. If it is enclosed or partially enclosed and presents risks such as poor ventilation, a buildup of exhaust fumes, low oxygen, or difficulty exiting in an emergency, it meets the definition of a confined space under UK regulations.

An attic is not usually a confined space, but it can become one if it is enclosed enough and contains serious risks such as poor ventilation, heat build-up, restricted access, or hazardous fumes. Its classification depends on the actual conditions and dangers present.

The first thing you must consider is whether entry can be avoided.

Under the Confined Spaces Regulations 1997, you must ask “Is it reasonably practicable to do the work without entering the confined space?” If the task can be done another way (for example, from outside, using remote tools, or redesigning the work), entry must not take place.

The difference depends on the level of danger and the controls required.

• Low-risk confined space: No foreseeable specified risks, stable atmosphere, and basic controls are sufficient.
• Medium-risk confined space: Specified risks could develop during work, so formal controls, monitoring, supervision, and planned rescue arrangements are needed.
• High-risk confined space: One or more specified risks are present or likely, such as toxic atmospheres or engulfment, requiring permits, specialist PPE, continuous monitoring, and dedicated rescue provision.

The higher the risk, the more robust the controls and rescue arrangements required.

A Safe System of Work (SSOW) for confined space entry is a planned, documented method that sets out how work will be carried out safely where confined space hazards cannot be avoided.

A SSOW includes:

• Risk assessment identifying the confined space hazards and specified risks
• Control measures to eliminate or reduce risk (for example ventilation, isolation, purging)
• Entry procedures, including permits, access controls, and supervision
• Competence and training requirements for everyone involved
• Atmospheric testing and monitoring arrangements
• Personal protective equipment (PPE) and emergency equipment
• Emergency and rescue arrangements, including rescue personnel and drills
• Clear roles and communication throughout the work

A SSOW explains exactly how confined space work will be done safely, from preparation through entry, work, and emergency response.

No. Not all confined spaces require a permit.

A permit is only needed when the confined space contains specified risks under the Confined Spaces Regulations 1997, such as toxic gases, low oxygen, fire or explosion risk, drowning, or entrapment. If no such risks are present, a permit is not legally required.

A confined space permit only lasts for the specific task and time period stated on the permit. It is valid only for that entry, must be closed when the work ends, and must be reissued if conditions, personnel, or risks change.

Atmospheric testing requires a suitable, calibrated gas detector capable of measuring the specific hazards present in the confined space.

Equipment includes:

• A portable multi-gas monitor (commonly measuring oxygen, flammable gases, and toxic gases such as carbon monoxide or hydrogen sulphide)
• Sampling tubes or probes for testing from outside the space before entry
• Bump test and calibration equipment to confirm the monitor is working correctly

When testing should be done:

• Before entry – to confirm the atmosphere is safe
• During entry – where conditions could change, using continuous or periodic monitoring
• After breaks or changes – if work stops, ventilation fails, or substances are introduced

Testing should be carried out by a competent person, and results must be considered as part of the Safe System of Work.

In a confined space, purging and ventilation are methods used to make the atmosphere safe to enter and work in.

Purging is the process of removing hazardous gases, vapours, fumes, or lack of oxygen from the space before entry, usually by flushing it with clean air or an inert gas. Its purpose is to displace contaminants and restore safe oxygen levels.

Ventilation is the continuous or ongoing supply of fresh air to the space, either naturally or mechanically, to prevent the build-up of dangerous atmospheres while work is taking place.

In a potentially explosive confined space, lighting must be designed to eliminate ignition risk.

Key requirements are:

• Explosion-protected (ATEX-rated) lighting suitable for the relevant zone classification (Zone 0, 1, or 2)
• Equipment certified to UKCA/ATEX standards, with the correct gas group and temperature class
• Low-voltage lighting where practicable to reduce ignition risk
• Sealed, robust fittings to prevent sparks, heat build-up, or damage
• Cabling and connections protected against impact, abrasion, and moisture
• Emergency or backup lighting where loss of light would increase risk

Ordinary site lights, temporary lamps, or non-rated torches must not be used in explosive atmospheres.

You should not use CO₂ fire extinguishers in confined spaces because they can rapidly displace oxygen, creating a risk of suffocation for anyone inside.

A breathing apparatus (BA) is respiratory protective equipment that provides the wearer with an independent supply of breathable air, rather than relying on the surrounding atmosphere.

In confined space work, BA is mandatory where:

• The atmosphere is unsafe or oxygen-deficient, or could become so
• Toxic gases, fumes, or vapours are present or may be released
• There is a risk of asphyxiation
• The atmosphere cannot be reliably made or kept safe by ventilation alone
• Rescue operations may be required in a hazardous atmosphere

BA must be suitable for the task, properly maintained, and worn only by trained and medically fit workers.

A “Top Man” or “Sentry” is the competent person stationed outside a confined space to protect those working inside.

Their duties include:

• Remaining outside the space at all times and not entering it
• Monitoring conditions and workers’ wellbeing
• Maintaining constant communication with entrants
• Controlling entry and exit, including permits where used
• Raising the alarm and initiating emergency procedures if something goes wrong
• Preventing unauthorised entry into the confined space

They must be trained, briefed on the Safe System of Work, and never distracted by other tasks.

Self-rescue is the procedure that enable a worker to leave a confined space immediately and without assistance if conditions become unsafe.

It is used when alarms sound, atmospheric conditions change, controls fail, or the worker feels unwell.

Lone working in a confined space may be permitted only where the risk is low, no specified risks are present or likely to develop, self-rescue is realistic, and effective communication, supervision, and emergency arrangements are in place.

Lone working is not acceptable in medium- or high-risk confined spaces, or where atmospheric hazards or assisted rescue may be required.

No. You cannot rely on the emergency services for a confined space rescue.

Under the Confined Spaces Regulations 1997, employers must have suitable and sufficient rescue arrangements in place before entry takes place. Emergency services should not be the planned rescue method, as they may not arrive in time or have the specialist equipment immediately available.

This means you must:

• Plan and provide on-site rescue arrangements
• Ensure rescuers are trained, equipped, and ready
• Have rescue equipment available immediately

Emergency services may assist after a rescue is initiated, but they do not replace the legal duty to plan for rescue.

A confined space rescue plan must be site-specific, practical, and in place before entry.

Under the Confined Spaces Regulations 1997, it must include:

• Rescue method – how a casualty will be removed without relying on the emergency services
• Trained rescue personnel – competent, available, and familiar with the space and risks
• Rescue equipment – appropriate and immediately available (e.g. harnesses, winches, breathing apparatus)
• Emergency communications – clear means to raise the alarm and coordinate rescue
• First aid arrangements – including provision for resuscitation where needed
• Access and egress details – how rescuers will safely enter (if required)
• Testing and rehearsal – regular practice drills and reviews to keep the plan effective

The plan must match the level of risk: higher-risk confined spaces require more robust and specialist rescue arrangements.

Dynamic Risk Assessment is the continuous, real-time assessment of risk while work is underway.

Once confined space work has started, it means workers must:

• Remain alert to changing conditions (atmosphere, heat, liquids, fumes, plant status)
• Monitor readings and controls (gas levels, ventilation, isolation)
• Stop work immediately if conditions deteriorate or controls fail
• Review and adjust the Safe System of Work where necessary
• Withdraw from the space if a new or increased specified risk arises

Dynamic assessment supplements the original risk assessment by recognising that confined space conditions can change rapidly.

There is no automatic legal requirement for a medical assessment before working in confined spaces, but it may be necessary depending on the risks and the role.

A medical assessment is usually required where workers:

• Use breathing apparatus or respiratory protective equipment
• Work in high-risk confined spaces
• Could be affected by heat, stress, physical exertion, or restricted escape
• Are part of a confined space rescue team

Employers must ensure workers are fit and competent for the work under the Confined Spaces Regulations 1997 and general health and safety law. In higher-risk situations, this often means confirming medical fitness as part of the risk assessment.

Confined space training teaches workers how to recognise confined spaces, understand the hazards, and follow safe entry and work procedures. It covers risk assessment, atmospheric testing, permits, emergency arrangements, and the use of safety equipment so that people can work safely and legally in confined spaces.

Confined space training involves learning how to identify confined spaces, understand the hazards, and follow safe systems of work. It includes risk assessment, atmospheric testing, safe entry procedures, permit use, PPE and equipment, communication methods, and emergency and rescue arrangements.

You can complete awareness-level confined space training online, which is valuable for helping workers understand the risks, legal duties, and safe working principles before any practical activity takes place.

Practical confined space training, including entry, equipment use, and rescue procedures, must be completed face-to-face to meet UK safety requirements.

A confined space course usually lasts around one day for an entry-level practical course, while awareness-level courses are shorter and can often be completed in under an hour online.

More advanced or rescue-focused courses may take two to three days, depending on the level of competence required.

Confined space training should be refreshed every 1–3 years, depending on the level of risk, how often the work is carried out, and whether there have been changes in equipment, procedures, or staff competence.

Employers must ensure workers remain competent, so refresher training may be required sooner if unsafe practices or new hazards are identified.