RAMS for Confined Space Entry: UK Guide to Safe Working

Confined spaces kill people who know what they are doing. That is what makes them so dangerous. The victims are not untrained labourers; they are experienced workers, supervisors, and (most commonly) the rescuers who rush in to help a fallen colleague. A safe atmosphere can become lethal in seconds. The only defence is a properly written RAMS backed by a genuine safe system of work.

This guide covers every critical section your confined space RAMS must include: gas testing protocols, ventilation requirements, permit to work procedures, communication plans, and the rescue plan that will determine whether a bad situation stays recoverable or turns fatal.

What is a Confined Space?

The legal definition comes from the Confined Spaces Regulations 1997. A confined space is any place that is substantially (though not necessarily entirely) enclosed, and where there is a reasonably foreseeable risk of serious injury from hazardous substances or conditions within the space or nearby.

Size is irrelevant. A large storage tank is still a confined space. A football-pitch-sized excavation can be a confined space if heavier-than-air gases accumulate. The defining factors are enclosure and the presence of foreseeable risk, not physical dimensions.

Common confined space examples include:

• Manholes and inspection chambers
• Sewers and drainage systems
• Storage tanks, silos, and vessels
• Excavations deeper than 1.2 metres
• Roof voids, ceiling spaces, and enclosed lofts
• Ducts, pipework, and flues
• Chambers, vaults, and pits

The hazardous conditions that make these spaces dangerous include oxygen depletion (biological or chemical processes consuming O2), toxic gas accumulation (H2S from decomposition, CO from engines or processes), flammable atmospheres (methane, petrol vapour, dust), engulfment by liquids or free-flowing solids, and excessive heat.

The Fatal Statistics

Confined spaces kill between 15 and 20 workers in the UK every year. The number has stayed stubbornly consistent for decades despite improvements in equipment, training, and regulation.

The most alarming statistic: roughly 60% of confined space deaths are rescuers. People who were never meant to enter the space, who saw a colleague collapse, and who entered on instinct without breathing apparatus. They died trying to help. This single fact should shape everything in your RAMS.

Many victims are experienced workers. They have entered the same space dozens of times without incident. The atmosphere was fine last Tuesday. But confined space atmospheres can change in seconds. A pocket of trapped gas shifts. Biological decomposition accelerates. A nearby process releases fumes. The space that was safe at 9am becomes lethal at 9:05am.

These deaths are preventable. Every single one. That is why the Confined Spaces Regulations 1997 place such strict duties on employers and the self-employed.

Confined Spaces Regulations 1997: Key Duties

The Regulations are short (only 6 substantive regulations) but the duties they impose are absolute. Three regulations matter most when writing your RAMS.

Regulation 4: Avoid entry where reasonably practicable. This is the first question your RAMS must answer. Can the work be done from outside? Remote cameras, long-reach tools, mechanical cleaning systems, and robotic inspection equipment mean that many tasks previously requiring entry can now be completed without anyone going inside. Your RAMS must demonstrate that you have considered alternatives and explain why entry is necessary.

Regulation 5: Safe system of work. If entry cannot be avoided, the work must follow a safe system of work. This is the core of your RAMS. It covers everything from pre-entry gas testing to the sequence of operations inside the space. The safe system must be documented, communicated to every person involved, and followed without deviation.

Regulation 6: Emergency arrangements. Suitable and sufficient arrangements for rescue must be in place before anyone enters the confined space. Not after. Not during. Before. This includes trained rescue personnel, pre-positioned equipment, and a tested communication system. If your rescue plan is "call 999", your RAMS is not compliant.

Writing the RAMS: Critical Sections

A confined space RAMS follows the same structure as any RAMS, but certain sections carry far more weight. Get these wrong and people die. There is no middle ground.

Gas Testing and Atmospheric Monitoring

Atmospheric testing is non-negotiable. Your RAMS must specify a minimum 4-gas monitor capable of detecting oxygen (O2), lower explosive limit (LEL), carbon monoxide (CO), and hydrogen sulphide (H2S). These four gases cover the most common confined space hazards. Depending on the specific environment, additional sensors may be needed (for example, SO2 near industrial processes).

Testing must happen at two stages. First, pre-entry testing: the atmosphere must be tested before the permit to work is issued. Test at multiple levels within the space (top, middle, bottom) because gases stratify by density. Second, continuous monitoring: the gas detector must remain active throughout the entire duration of work. It should be worn by the entrant with audible and visual alarms enabled.

Your RAMS must state the acceptable atmospheric levels:

• Oxygen (O2): 19.5% to 23%. Normal air is 20.9%. Below 19.5% indicates oxygen depletion. Above 23% creates a severe fire and explosion risk.
• LEL (Lower Explosive Limit): Below 10% of LEL. Any reading above 10% means immediate evacuation.
• Carbon monoxide (CO): Below 20 ppm. The workplace exposure limit is 20 ppm (8-hour TWA). CO is odourless and colourless, making it impossible to detect without instruments.
• Hydrogen sulphide (H2S): Below 5 ppm. H2S smells like rotten eggs at low concentrations but destroys the sense of smell at higher levels, so workers can stop smelling it just as it becomes lethal.

If any reading falls outside acceptable limits, the RAMS must require immediate evacuation and reassessment. No exceptions, no judgement calls on site.

Ventilation

Forced mechanical ventilation must be specified in your RAMS. Natural ventilation is almost never sufficient for confined spaces. A powered fan or blower should supply fresh air continuously throughout the work, positioned to create a flow pattern that pushes contaminated air out of the space.

Your RAMS must include a critical prohibition: never use oxygen to ventilate a confined space. Enriching the atmosphere with pure oxygen creates an extreme fire and explosion hazard. Clothing, hair, and materials become highly flammable in oxygen-enriched atmospheres. This has caused multiple fatalities and must be explicitly prohibited in the method statement.

Permit to Work

A permit to work (PTW) is mandatory for confined space entry. The permit is a formal document that authorises specific people to carry out specific work in a specific confined space during a specific time period. It is not a one-off form filed away; it is a live control document.

Your RAMS should specify the permit to work process: who issues it (a competent, authorised person, not the entrant themselves), what pre-entry checks must be completed before issue (atmospheric test results recorded, rescue equipment confirmed in position, top person in place), the time limit (permits should be limited to one shift maximum and re-issued for each new entry), and formal cancellation on completion of work or if conditions change.

Communication

The RAMS must require a trained top person (attendant) stationed at the entry point at all times while anyone is inside the confined space. This person must never enter the space, regardless of what happens inside. Their role is to maintain communication, monitor conditions, summon rescue, and control access.

Continuous visual or radio contact must be maintained between the entrant and the top person. Where line of sight is not possible (bends in pipework, deep shafts), intrinsically safe radios or wired communication systems are required. Your RAMS should define agreed alarm signals: a specific signal to evacuate immediately, a check-in frequency (for example, verbal confirmation every 5 minutes), and a procedure for loss of communication (treat as an emergency).

Rescue Plan

The rescue plan is the most critical section of any confined space RAMS. It is also the section most commonly left vague. Phrases like "rescue will be carried out by emergency services" or "dial 999 in an emergency" are not compliant with Regulation 6. The fire service may take 15 to 30 minutes to arrive. A person exposed to an oxygen-depleted atmosphere will suffer brain damage within 4 minutes and death shortly after.

Your rescue plan must include: a trained rescue team on standby at the site (not on call elsewhere), self-contained breathing apparatus (SCBA) available and ready to use, a winch and tripod system for vertical entry spaces, trained first aiders with oxygen resuscitation equipment, and a clear procedure that prohibits entry without breathing apparatus, even in an emergency.

The rescue team must be briefed before work starts. They must know the layout of the space, the hazards present, the number of people inside, and the extraction route. Equipment must be pre-positioned and checked, not stored in a van 200 metres away.

PPE Requirements

PPE for confined space entry goes beyond standard site requirements. Your RAMS should specify a full-body harness with an attached lifeline connected to a retrieval system (tripod and winch for vertical spaces, horizontal lifeline for horizontal spaces). This allows the rescue team to extract a casualty without entering the space.

Respiratory protective equipment (RPE) depends on the hazard assessment. For spaces where the atmosphere is known to be safe and continuously monitored, an emergency escape breathing device (EEBD) may be sufficient as a backup. For spaces where the atmosphere is or may become hazardous, self-contained breathing apparatus (SCBA) is required for entry. Never rely on filter-type respirators in confined spaces, as they do not protect against oxygen depletion.

The Rescue Plan: Why 60% of Deaths Are Rescuers

This section deserves its own heading because it is the single most important factor in confined space fatalities. The pattern is always the same. A worker collapses inside a confined space. A colleague at the entrance sees it happen. Instinct takes over. They climb in to help. Within seconds, they are unconscious too. Sometimes a third person follows. Sometimes a fourth.

The HSE has documented cases where more rescuers died than original entrants. The toxic atmosphere that incapacitated the first person is still there. It does not care about good intentions. Carbon monoxide does not distinguish between the worker and the hero.

Your RAMS must address this directly. It must state, in unambiguous language, that entry without breathing apparatus is prohibited at all times, including during an emergency rescue. This instruction must be reinforced during the pre-entry briefing. Every person on site must understand it. The top person must be trained to prevent spontaneous rescue attempts and to activate the planned rescue procedure instead.

Pre-positioned rescue equipment makes the difference. When the tripod is already in place, the winch is attached, and the harness lifeline is connected, extraction can begin immediately without anyone else entering the space. When the equipment is in a storage box somewhere on site, people die while others search for it.

The rescue team must be briefed before work starts, not after an incident. They need to know the space dimensions, the access and egress points, the hazards identified, and the exact steps to follow. A rescue plan that only exists on paper is not a rescue plan.

Generate Your Confined Space RAMS

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Related Guides

For more on the topics covered in this guide, see our related resources:

• Permit to Work Guide
• Construction Phase Plan Guide
• What is a RAMS?
• Safe System of Work Guide

Types of Confined Space Hazard

Your RAMS must identify the specific hazards present in the confined space. Generic hazard lists are not sufficient. Each space is different, and the hazards can change between entries. The five main categories below cover the majority of confined space incidents in the UK.

Toxic Atmosphere

A toxic atmosphere is the single most common cause of confined space fatalities. The danger is that many toxic gases are invisible and odourless, or cause olfactory fatigue so quickly that workers stop noticing the smell within seconds.

Hydrogen sulphide (H2S) is common in sewers, drains, and any space where organic material decomposes. It smells of rotten eggs at low concentrations, but at 10 ppm the olfactory nerve becomes paralysed and the worker can no longer detect the gas. At 100 ppm, exposure for 30 to 60 minutes can be fatal. In sewer work, concentrations can spike to several hundred ppm without warning.

Carbon monoxide (CO) is generated by petrol and diesel engines, fires, welding, cutting, and any incomplete combustion process. It is completely odourless and colourless. CO binds to haemoglobin roughly 200 times more effectively than oxygen, meaning even low concentrations accumulate rapidly in the bloodstream. Running a petrol generator near a confined space opening, or using a petrol-driven pump inside a space, has killed multiple workers in the UK.

Methane (CH4) is produced by the decomposition of organic material. It is found in sewers, landfill sites, silos storing organic materials, and any space connected to biological processes. Methane is both an asphyxiant (displacing oxygen) and flammable, creating a dual hazard. Its explosive range is between 5% and 15% in air.

Your RAMS should specify the Workplace Exposure Limits (WELs) for every gas likely to be present, state the alarm set-points on your gas detector, and define the action to be taken at each alarm level.

Oxygen Depletion

Normal air contains approximately 20.9% oxygen. Oxygen-depleted atmospheres occur when oxygen is consumed (by rusting, biological activity, or combustion) or displaced by another gas (nitrogen purging, CO2 from fermentation, argon from welding).

The effects are progressive and insidious. Below 19.5%, judgement and coordination begin to deteriorate, often without the worker realising. Below 16%, consciousness is impaired and the worker may be unable to self-rescue. Below 6%, death occurs within minutes. The critical danger is that oxygen depletion gives almost no warning. There is no smell, no visible indicator, and the worker's declining cognitive function prevents them from recognising the danger.

Oxygen Enrichment

Oxygen enrichment occurs when oxygen levels exceed 23.5%. This creates an extreme fire and explosion risk. Materials that would not normally ignite, including clothing, can catch fire easily and burn with intense ferocity. Grease and oil can spontaneously combust. An oxygen-enriched atmosphere turns a minor ignition source into a catastrophic fire.

Oxygen enrichment commonly results from leaking oxy-acetylene equipment, incorrect purging procedures, or (critically) from using oxygen to ventilate a confined space. Never ventilate a confined space with oxygen. Always use fresh air. This point must be stated explicitly in your RAMS because the mistake continues to be made on UK sites.

Engulfment

Engulfment occurs when a worker is buried or submerged by a free-flowing solid or liquid. Grain silos are the most well-known example, where bridged grain can collapse and bury a worker in seconds. Once submerged to waist depth in grain, self-rescue is virtually impossible due to the pressure exerted by the material.

Other engulfment hazards include hoppers containing sand, cement, or aggregate, and interceptors that can fill rapidly with water or sewage. Your RAMS must specify lockout/tagout procedures for all feed mechanisms and confirm that discharge valves are isolated before entry.

Entrapment

Entrapment hazards exist where the internal geometry of the space can trap a worker or where mechanical equipment could activate. Spaces that narrow towards the bottom (such as V-shaped hoppers) can wedge a worker who slips, making rescue extremely difficult.

Mechanical hazards include augers, agitators, conveyors, and mixing blades that could restart during the entry. Isolation must go beyond simply switching off the equipment. Your RAMS must require full lockout/tagout (LOTO) with personal locks applied by each person inside the space. Stored energy (hydraulic pressure, spring tension, elevated components) must be dissipated and confirmed safe before entry begins.

Emergency Rescue Equipment

Regulation 6 of the Confined Spaces Regulations 1997 requires suitable and sufficient rescue arrangements to be in place before entry begins. "Suitable" means matched to the specific space, the hazards present, and the number of entrants. The following equipment categories should be assessed and documented in every confined space RAMS.

Tripod and Winch

A tripod and winch system is the standard rescue arrangement for vertical entries up to approximately 20 metres deep. The tripod sits over the opening and the winch allows a single rescuer to raise an incapacitated worker without entering the space. Every entrant wears a full body harness connected to the winch line. The system must be load-tested, inspected before each use, and rated for the weight of the heaviest entrant plus their equipment.

Davit Arm

A davit arm provides a fixed anchor point for deeper entries or where the opening is offset from the vertical line of descent. Davit arms bolt to a permanent base plate near the entry point and can handle greater depths than a portable tripod. They are common on tanks, vessels, and deep manholes where regular entry is required.

Self-Contained Breathing Apparatus (SCBA)

SCBA provides an independent air supply and is required when the atmosphere is immediately dangerous to life or health (IDLH), or when a powered air-purifying respirator (PAPR) cannot provide adequate protection. This includes oxygen-deficient environments, spaces containing gases that would overwhelm filter capacity, and rescue operations where the atmosphere is unknown. All SCBA users must hold current certification and practise donning drills regularly.

Emergency Escape Breathing Device (EEBD)

An EEBD provides a short-duration air supply, typically 5 to 10 minutes, intended solely for self-rescue. It is not a substitute for SCBA or BA and is not designed for entry into a hazardous atmosphere. An EEBD allows a worker to escape if the atmosphere deteriorates unexpectedly during an entry where initial gas testing showed safe conditions. Every entrant should have an EEBD within immediate reach.

First Aid Equipment

First aid equipment must be positioned at the entry point, not inside the space and not in a distant site welfare cabin. As a minimum, this should include oxygen resuscitation equipment, a trauma kit, and a defibrillator where the risk assessment warrants it. The standby person must be trained in its use. Response time is critical in confined space casualties, and having equipment immediately to hand can be the difference between recovery and death.

Communication Equipment

Reliable communication equipment between the entrant, the standby person, and the rescue team is essential. In simple horizontal entries, voice communication may be adequate. For deeper or more complex spaces, two-way radios or hardwired intercom systems are required. Where the confined space has a potentially flammable atmosphere, all electronic communication equipment must be intrinsically safe (IS rated) to prevent it becoming an ignition source. Standard mobile phones and consumer radios must never be used in these conditions.

Real Case Studies: What Went Wrong

The following cases are drawn from HSE investigation reports. They are not included for shock value. Each one illustrates a specific, recurring failure mode that your RAMS must address.

Case 1: Sewer Entry Without Breathing Apparatus

Two workers were carrying out maintenance in a sewer. The first worker descended without breathing apparatus and collapsed almost immediately. The standby person entered to attempt rescue, also without BA. Both workers died. The atmosphere contained lethal levels of hydrogen sulphide that had accumulated since the last entry, which had tested clear.

Key lesson: The standby person must never enter the confined space under any circumstances. Their role is to raise the alarm and initiate the emergency rescue plan. This must be drilled, rehearsed, and stated in absolute terms in your RAMS. Instinct will tell them to go in. Training and procedure must override that instinct.

Case 2: Nitrogen Purging Without Atmosphere Testing

A worker entered a storage tank that had been purged with nitrogen to remove flammable vapours. The purging was successful in removing the vapour hazard, but the tank was not ventilated with fresh air afterwards and no atmosphere test was conducted before entry. The worker was overcome by oxygen depletion within seconds. Nitrogen is odourless and gives no physiological warning. The worker lost consciousness before reaching the bottom of the access ladder.

Key lesson: Purging removes one hazard but creates another. Your RAMS must include a mandatory step between purging and entry: ventilate the space with fresh air, then test the atmosphere with a calibrated multi-gas detector. A space that has been purged is not the same as a space that is safe to enter.

Case 3: Carbon Monoxide from Welding in an Unventilated Vessel

A welder was working inside a large steel vessel with forced ventilation initially in place. The ventilation fan was creating noise that made communication difficult, so it was turned off. The welder continued working. Carbon monoxide from the welding process accumulated rapidly in the unventilated space. The welder lost consciousness and died before the standby person recognised the problem.

Key lesson: Ventilation is not optional and cannot be traded off against convenience. If ventilation makes communication difficult, the solution is better communication equipment, not less ventilation. Your RAMS must state clearly that ventilation must run continuously during the entire entry and that no one has the authority to turn it off while the space is occupied. Continuous atmospheric monitoring with audible alarms provides the secondary safeguard.

Frequently Asked Questions

Is a large open-top tank a confined space?

It can be. The legal definition does not require the space to be fully enclosed. A large open-top tank is substantially enclosed if gases could accumulate within it. If the tank contains (or recently contained) a hazardous substance, or if heavier-than-air gases could settle in the bottom, it meets both criteria of the definition: substantial enclosure and foreseeable risk. Treat it as a confined space, carry out a risk assessment, and apply the Confined Spaces Regulations 1997.

What if the gas test shows clear, can we skip breathing apparatus?

A clear pre-entry gas test does not guarantee the atmosphere will remain safe. Conditions can change during the entry due to work activities (welding, grinding, painting), disturbance of residues, or changes in ventilation. Your RAMS should specify whether BA is required based on the worst foreseeable conditions, not the best-case reading. If BA is downgraded based on initial test results, continuous atmospheric monitoring with automatic alarms must be in place, and BA must be available at the entry point for immediate use if conditions change.

How often should we re-test the atmosphere?

Best practice is continuous monitoring throughout the entry using a personal multi-gas detector worn by each entrant. If continuous monitoring is not available, the atmosphere must be re-tested at intervals specified in your RAMS, typically every 15 to 30 minutes at minimum. Additional tests should be carried out after any break in work, after any process change (such as starting a new welding run), and if the ventilation system is interrupted for any reason.

Can one person enter a confined space?

The Regulations do not explicitly prohibit solo entry, but Regulation 6 requires suitable rescue arrangements, which in practice means at least a trained standby person stationed at the entry point at all times. The standby person does not enter the space but maintains communication, monitors conditions, and activates the rescue plan if needed. There is no scenario where a worker should be inside a confined space with nobody aware of their location.

What qualifications does the confined space rescue team need?

Rescue team members should hold a City & Guilds 6150 confined space qualification (or equivalent), covering medium and high risk categories as appropriate to the spaces they will work in. They must be trained in the use of all rescue equipment specified in the RAMS, including SCBA, tripod/winch systems, and casualty handling in restricted spaces. They must practise rescue drills at realistic intervals. A rescue team that has not drilled in six months is not a rescue team. Your RAMS must record the names, qualifications, and drill dates for every member of the rescue team.

Authority Sources and Further Reading

The following external sources provide the authoritative guidance that underpins this article. All should be referenced during your confined space risk assessment.

• HSE L101: Safe Work in Confined Spaces is the Approved Code of Practice (ACoP) for the Confined Spaces Regulations 1997. It carries special legal weight: if you are prosecuted for a breach and you did not follow the ACoP, you must prove your alternative approach was equally effective.
• HSE INDG258: Safe Work in Confined Spaces is the free, simplified guidance leaflet from HSE. It provides a practical overview suitable for toolbox talks and site briefings. It does not replace L101 but is a useful introduction for workers who need to understand the fundamentals.
• BS 7671 (IET Wiring Regulations) applies where electrical work is carried out in confined spaces. Requirements include reduced voltage supplies, RCD protection, and specific cable management provisions. Section 706 deals with restrictive conductive locations, which includes many confined spaces.
• City & Guilds 6150 Confined Space Qualifications is the most widely recognised confined space training framework in the UK. It covers low, medium, and high risk categories and is the qualification your rescue team members should hold as a minimum standard.

For related topics covered in depth on this site, see the following guides:

• RAMS for Excavation and Trenching covers trench shoring, ground conditions, and underground services, all of which overlap with confined space work in excavations.
• RAMS for Hot Works details fire watch procedures, hot work permits, and the additional controls required when welding or cutting in enclosed environments.
• COSHH Assessment for Welding Fumes explains how to assess and control exposure to welding fume, including the specific considerations for welding inside confined spaces where fume concentrations build rapidly.
• Permit to Work Guide covers the full permit to work process, including how confined space entry permits integrate with hot work permits and isolation certificates.
• Construction Phase Plan Guide explains how confined space work should be documented within the wider CDM 2015 framework, including principal contractor duties for coordinating confined space entries across multiple trades.