Risk Assessments · Mandatory · Pre-Construction

RAMS — Confined Space Entry

This RAMS covers entry into confined spaces such as tanks, manholes, chambers, and voids where there is a foreseeable risk of serious injury from hazardous atmospheres, engulfment, or entrapment. It mandates atmospheric monitoring, permit-to-work systems, trained rescue teams on standby, and communication protocols. Entry must be avoided unless there is no reasonably practicable alternative.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. Confined Spaces Regs 1997 remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.

Legal basis	Confined Spaces Regulations 1997
Key duty (Reg 4)	Avoid entry to a confined space if reasonably practicable
Rescue requirement (Reg 5)	Mandatory arrangements must be in place before any entry
Permit to work	Required for all entries to a confined space
Standby person	Must remain outside the confined space at all times — NEVER enter
Atmospheric testing	Multi-gas detector (O2, flammable, toxic) required before entry and continuously during work
Enforcing authority	Health and Safety Executive (HSE)

1. What It Covers

Confined space entry is the highest-risk activity covered in this series. Workers die from atmospheric conditions that were not identified before entry, or from failed rescue attempts where untrained personnel enter the space to help a collapsed colleague and are themselves overcome by the same hazard.

The Confined Spaces Regulations 1997 impose a strict hierarchy: avoid entry entirely if reasonably practicable; if entry is unavoidable, implement a safe system of work; and ensure that rescue arrangements are in place before anyone enters. Every element of the safe system must be planned, documented, and communicated before the first entry takes place.

Multiple fatalities occur every year — many involve failed rescues

A significant proportion of confined space deaths in the UK involve bystander rescues — colleagues who enter the space to help a casualty without breathing apparatus or training, and are overcome by the same atmosphere. The instinct to help is natural, but unplanned entry during an emergency is one of the most lethal actions on a construction site. Regulation 5 exists specifically to prevent this: rescue arrangements must be established before the first entry, not improvised during an emergency.

2. What Is a Confined Space?

A confined space is not defined by size alone. Under the Confined Spaces Regulations 1997, a space is classified as confined when two criteria are both met: (a) the space is substantially enclosed (though not necessarily entirely closed), and (b) one or more of the specified risks is present or could reasonably be foreseen to arise.

Many spaces that do not appear ‘confined’ in the everyday sense of the word fall within the legal definition because a specified risk is present. Conversely, a small cupboard with no specified risk is not a confined space under the Regulations.

Construction examples of confined spaces

Manholes, drainage culverts, storage tanks, water tanks, sewers, tunnels, shafts, voids between walls, deep basements with limited ventilation, ceiling voids, ductwork, partially excavated trenches where heavier-than-air gases may accumulate, and any chamber or enclosure where the atmosphere may differ from normal ambient air.

The six specified risks

Specified risk	Description	Construction examples
Flammable substance	Gas, vapour, or mist present at a concentration that could ignite or explode	Petrol interceptors, tanks previously containing solvents, sewers with methane accumulation
Excess oxygen (>21%)	Oxygen-enriched atmosphere increasing fire and explosion risk	Spaces near oxygen supply lines, welding and cutting operations in enclosed areas
Oxygen deficiency (<18%)	Atmosphere with insufficient oxygen to sustain consciousness and life	Spaces where oxygen has been displaced by nitrogen purging, rusting steel vessels, biological decomposition in manholes
Toxic substance	Gas, fume, or vapour present at a concentration harmful to health	Hydrogen sulphide in sewers, carbon monoxide from engines or heating, solvent vapour in tanks
Engulfment	Risk of being trapped or buried by a free-flowing solid or liquid	Grain silos, hoppers, partially flooded chambers, excavations where water ingress is possible
Loss of consciousness from heat	Elevated temperature causing heat stress, collapse, or loss of consciousness	Boiler chambers, steam tunnels, enclosed plant rooms with running machinery

3. Safe System of Work

Where entry to a confined space cannot be avoided, a safe system of work must be established before any person enters. The system must address every foreseeable risk and must be documented, communicated to all personnel involved, and enforced throughout the duration of the work. The following table sets out the steps in sequence.

Step	Action	Timing
1	Avoid entry — confirm that the work cannot be carried out from outside the space	Planning stage, before any preparation for entry
2	Appoint a competent supervisor responsible for the entry	Before work begins on site
3	Ensure all workers are suitable — trained, medically fit, and briefed on the specific hazards	Before personnel are assigned to the task
4	Isolate the space — lock off mechanical and electrical systems, blank pipework, close valves	Before any person enters the space
5	Clean and purge the space — remove residues, flush with clean air or inert gas as appropriate	After isolation, before atmospheric testing
6	Test the atmosphere — multi-gas detector for oxygen, flammable gases, and toxic gases	After purging, before entry, and continuously during work
7	Provide mechanical ventilation — forced air supply to maintain a safe atmosphere	Before entry and continuously during occupancy
8	Establish lighting and communications — safe lighting within the space and two-way communication with the standby person	Before entry
9	Appoint a standby person — trained individual who remains outside the space at all times	Before the permit is issued
10	Implement the permit to work — formal written authorisation for each entry, time-limited and task-specific	Immediately before each entry
11	Confirm rescue arrangements are in place — equipment tested, rescuers briefed, emergency services notified if appropriate	Before the first entry of the shift

4. Rescue Plan

“No person at work shall enter or carry out work in a confined space unless there have been prepared...suitable and sufficient arrangements for the rescue of persons in the event of an emergency.”— Confined Spaces Regulations 1997, Regulation 5

Regulation 5 is absolute: rescue arrangements must be in place before any person enters a confined space. A rescue plan that exists only on paper, with no equipment on site and no trained rescuers available, does not satisfy the regulation. The following table sets out the required elements.

Element	Required content
Named rescuer(s)	Identified individuals trained in confined space rescue, present on site during every entry
Rescue method	Specified as self-rescue, non-entry rescue (retrieval from outside), or entry rescue — in that order of preference
Rescue equipment on site	Retrieval harness and tripod, breathing apparatus, resuscitation equipment, stretcher, and communication devices — all on site, inspected, and ready for immediate use
Communication method	Defined method for the entrant to raise the alarm and for the standby person to summon rescue — e.g. two-way radio, visual signal, hard-wired intercom
Emergency services	Local emergency services notified of the work if appropriate; access route to the confined space identified and kept clear; site address and grid reference available
Resuscitation provision	Trained first aider with oxygen resuscitation equipment available on site for the duration of the entry
Tested before first use	The entire rescue plan must be practiced or tested before the first entry to confirm that it works — equipment functions, rescuers know their roles, and the procedure can be executed within a survivable timeframe

Non-entry rescue is always preferred over entry rescue

Where the geometry of the space allows it, non-entry rescue — using a retrieval harness and tripod or davit arm to extract the casualty without anyone else entering the space — is always the preferred method. Entry rescue places the rescuer at the same risk as the casualty and should only be planned where non-entry rescue is not feasible. Every rescue plan should default to non-entry rescue unless there is a documented reason why it cannot be used.

5. Common Mistakes

No atmospheric testing before entry

The atmosphere inside a confined space cannot be assessed by sight or smell. Hydrogen sulphide deadens the sense of smell at high concentrations, and oxygen-deficient air is invisible and odourless. Multi-gas testing with a calibrated detector is required before every entry and must continue throughout the work. Skipping this step is the single most common cause of confined space fatalities.

Standby person enters the space

The standby person exists to raise the alarm and coordinate rescue from outside. If they enter the space — whether to assist a casualty or for any other reason — no one remains to summon help. Multiple-fatality incidents frequently follow this pattern: the entrant collapses, the standby person enters to help, and both are overcome. The rule is absolute: the standby person must NEVER enter the confined space.

No permit issued for each entry

A permit to work is required for every individual entry to a confined space. A permit issued in the morning does not cover re-entry after a lunch break or a shift change. Each permit must be time-limited, task-specific, and signed by the authorising supervisor. Re-entry without a fresh permit is a breach of the safe system of work.

Rescue equipment absent or untested

Having rescue equipment listed on the method statement but not physically present on site — or present but never tested — provides no protection. Retrieval harnesses, tripods, breathing apparatus, and resuscitation equipment must be on site, inspected, and confirmed functional before the first entry. A rescue plan that has never been practiced is a plan that will fail under pressure.

Treating a deep manhole as "not really confined"

A common and dangerous assumption. A manhole that is several metres deep, with limited natural ventilation, meets both criteria of a confined space: it is substantially enclosed, and the risk of oxygen depletion or toxic gas accumulation is foreseeable. The fact that it has an open top does not remove it from the scope of the Regulations. Any substantially enclosed space where a specified risk is present — or could foreseeably arise — must be treated as a confined space.

6. Frequently Asked Questions

What training is required for confined space entry?▾

All personnel involved in confined space work must receive adequate training. As a minimum, entrants must be trained in the hazards of confined spaces, the use of gas detection equipment, emergency procedures, and the use of any personal protective equipment required. Rescue personnel must hold a recognised confined space rescue qualification and must have practiced the rescue procedure specific to the space being entered. Supervisors must be competent to assess risk, manage the permit system, and take charge in an emergency. Training must be refreshed at appropriate intervals — typically annually — and records must be maintained.

Can a ventilated space cease to be a confined space?▾

Not automatically. Mechanical ventilation reduces the risk of atmospheric hazards, but it does not remove a space from the scope of the Regulations. If the space is substantially enclosed and a specified risk could foreseeably arise — including if the ventilation were to fail — it remains a confined space. Ventilation is a control measure within the safe system of work, not a reclassification mechanism. The space must continue to be treated as confined, with permits, atmospheric testing, standby persons, and rescue arrangements maintained throughout.

Does a permit to work replace the need for RAMS?▾

No. A permit to work and a risk assessment and method statement serve different purposes and both are required. The RAMS identifies the hazards, assesses the risks, and sets out the method of work and control measures. The permit to work is the formal authorisation for a specific entry at a specific time, confirming that all elements of the safe system are in place. The RAMS informs the content of the permit; the permit authorises the entry. One does not replace the other.

What gas testing equipment is required?▾

A multi-gas detector capable of simultaneously measuring oxygen concentration, flammable gas levels (as a percentage of the lower explosive limit), and at least one toxic gas — typically hydrogen sulphide or carbon monoxide, depending on the environment. The detector must be intrinsically safe for use in potentially flammable atmospheres, currently calibrated, and tested with a bump test before each use. Personal gas monitors should be worn by each entrant. Pre-entry testing must be carried out using a remote sampling probe to test the atmosphere at multiple levels within the space before anyone enters.

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