Permits to Work · Mandatory · Construction

Permit to Work — Confined Space Entry

The Confined Space Entry Permit controls access to tanks, chambers, manholes, and other enclosed areas where a hazardous atmosphere, engulfment, or entrapment risk exists. It requires atmospheric monitoring before and during entry, a trained standby person, rescue equipment on site, and a defined communication protocol. Entry must not proceed until all permit conditions are satisfied.

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.

Definition	A space that is substantially enclosed (though not necessarily entirely closed) AND where one or more specified risks are present or could foreseeably arise
Key principle	Avoid entry entirely if reasonably practicable — Confined Spaces Regulations 1997, Regulation 4
Rescue first	Suitable and sufficient rescue arrangements must be in place BEFORE any person enters — Regulation 5
Standby person	Must remain outside the confined space at all times and must NEVER enter the space under any circumstances
Atmospheric testing	Multi-gas detector measuring O2 (19.5–23.5%), CO, H2S, and LEL — tested before entry and monitored continuously during work

1. Why Confined Space Entry Demands the Highest Level of Control

Confined space entry is consistently one of the most lethal activities in the construction industry. Workers die because the atmosphere inside the space was not tested before entry, because rescue arrangements were not in place, or because untrained bystanders entered the space to help a collapsed colleague and were themselves overcome by the same hazard. The Confined Spaces Regulations 1997 impose the strictest hierarchy of control of any workplace regulation: avoid entry if reasonably practicable; if entry is unavoidable, implement a documented safe system of work; and ensure that rescue arrangements are established before the first person enters.

The confined space entry permit is the formal mechanism through which this safe system of work is authorised and controlled. It goes beyond the generic PTW by requiring atmospheric testing results, confirmed rescue arrangements, a named standby person, and continuous monitoring throughout the duration of the entry. Every element must be verified at the point of work before the permit is issued — not assumed, not documented from a previous shift, but physically confirmed for that specific entry.

The legal framework combines the Confined Spaces Regulations 1997 (the primary legislation), the Management of Health and Safety at Work Regulations 1999 (risk assessment duty), CDM 2015 (contractor and principal contractor duties), and the HSE Approved Code of Practice L101 (Safe work in confined spaces). Non-compliance with Regulation 4 or Regulation 5 is a criminal offence, and prosecutions following confined space fatalities routinely result in significant fines and, in serious cases, imprisonment of individuals.

Never rely on the emergency services as your rescue plan

A significant number of confined space fatalities involve failed or improvised rescues. Regulation 5 requires that rescue arrangements are suitable and sufficient and in place before entry. Calling 999 is not a rescue plan. Emergency services may take 15 to 30 minutes or longer to arrive, and they may not have the specialist confined space rescue equipment or training for the specific space. On-site rescue capability — with trained rescuers, tested equipment, and a practiced procedure — must be established before the first entry of every shift. The rescue plan must be capable of extracting a casualty within a survivable timeframe.

2. Confined Space PTW Critical Checks

The confined space entry permit must contain the following fields. Each must be completed, verified at the point of work, and signed before any person enters the space. These checks represent the minimum standard required by the Confined Spaces Regulations 1997 and the HSE Approved Code of Practice L101.

Field	Required content
Space identification and definition	Unique identification of the confined space (location, reference number); confirmation that the space meets the legal definition (substantially enclosed with one or more specified risks present or foreseeable); description of the specified risks identified
Avoidance check (Regulation 4)	Documented confirmation that entry cannot be avoided — that the work cannot be carried out from outside the space by alternative means such as remote cameras, long-reach tools, or robotic equipment
Atmospheric test results	Pre-entry test results recorded on the permit: oxygen concentration (safe range 19.5% to 23.5%), flammable gas as percentage of LEL (must be below 10% LEL), carbon monoxide, hydrogen sulphide, and any other toxic gas specific to the environment; instrument serial number and calibration date recorded
Continuous atmospheric monitoring	Confirmation that continuous atmospheric monitoring will be maintained throughout the entry using personal multi-gas detectors worn by each entrant, with audible and visual alarms set to appropriate trigger levels
Mechanical ventilation	Confirmation that forced-air mechanical ventilation is in place and operational; airflow direction and rate specified; confirmation that ventilation will run continuously throughout the entry and cannot be inadvertently switched off
Isolations	All mechanical, electrical, hydraulic, pneumatic, and process isolations identified and confirmed locked off; pipework blanked or disconnected; valves locked closed; electrical supplies isolated at source and proved dead; isolation schedule attached to the permit
Named standby person	Named individual appointed as the standby person; confirmed trained in the emergency procedure; confirmed present at the entry point with communication equipment; explicit instruction that the standby person must NEVER enter the space
Rescue plan confirmed in place	Rescue method specified (self-rescue, non-entry retrieval, or entry rescue); rescue equipment on site and inspected (retrieval harness, tripod/davit, breathing apparatus, resuscitation equipment); named rescue team members confirmed on site and briefed
Respiratory protective equipment (RPE)	Type of RPE specified based on the atmospheric hazards identified; confirmed face-fit tested for each entrant; confirmed adequate supply of breathing air for the planned duration plus a safety margin; emergency escape sets available
Duration limit	Maximum time permitted inside the space for each entry; factors include air supply duration, heat stress limits, fatigue, and task complexity; permit must be closed and re-issued for each new entry even within the same shift

3. Common Mistakes

No atmospheric testing before entry

The atmosphere inside a confined space cannot be assessed by sight, smell, or previous experience. Hydrogen sulphide deadens the sense of smell at dangerous concentrations. Oxygen-deficient air is invisible and odourless. A person entering an oxygen-depleted space can lose consciousness within seconds without any warning. Multi-gas testing with a calibrated detector is mandatory before every entry — not just the first entry of the day, but every individual entry.

Standby person enters the space to help a casualty

This is the single most common cause of multiple fatalities in confined spaces. The standby person exists to raise the alarm and coordinate the rescue from outside the space. If they enter, no one remains to summon help, and the standby person is exposed to the same hazard that incapacitated the original entrant. The rule is absolute and non-negotiable: the standby person must NEVER enter the confined space, regardless of what is happening inside.

Rescue plan exists on paper but not on site

A rescue plan that lists equipment and procedures in the method statement but has no physical presence on site provides no protection. The retrieval harness, tripod, breathing apparatus, and resuscitation equipment must be physically present at the entry point, inspected, and confirmed functional before the first entry. Rescue team members must be on site, briefed, and have practiced the specific rescue procedure for the space being entered.

Single permit used for multiple entries across a shift

A permit to enter a confined space authorises a single entry for a defined period. If the entrant exits the space — for a break, a shift change, or any other reason — the permit must be closed and a new permit issued before re-entry. Conditions inside a confined space can change rapidly: gas may accumulate, ventilation may fail, or the atmosphere may be altered by work in adjacent spaces. Each new entry requires fresh atmospheric testing and a fresh permit.

Space not recognised as confined

Many spaces that do not look confined in the everyday sense of the word meet the legal definition. Deep manholes with open tops, ceiling voids, ductwork, partially enclosed plant rooms, and deep excavations where heavier-than-air gases may accumulate all qualify as confined spaces if a specified risk is present or foreseeable. The assessment must be based on the legal definition — substantially enclosed plus a specified risk — not on whether the space feels enclosed.

4. Related Documents

The confined space entry permit is the most stringent permit type in the PTW system. It connects to the following documents.

Document	Relationship
E1 — Generic PTW	The overarching permit-to-work framework. The confined space permit follows the same lifecycle but adds atmospheric testing, standby person, and rescue arrangements as mandatory elements.
E2 — Hot Works PTW	Where hot works are carried out inside a confined space, both permits are required. The hot works permit controls the fire risk; the confined space permit controls the atmospheric and access risks. The combined risk of fire in an oxygen-enriched or flammable atmosphere must be explicitly assessed.
E5 — Electrical Isolation PTW	Electrical equipment inside a confined space must be isolated before entry. The electrical isolation permit provides the formal lock-out/tag-out record that feeds into the confined space permit isolation schedule.
B5 — Confined Space RAMS	The risk assessment and method statement for confined space work. The RAMS identifies the specified risks, sets out the safe system of work, and defines the rescue method. The permit confirms that all elements are in place for each individual entry.
B1 — Generic Site Risk Assessment	The site-wide risk assessment should identify all confined spaces on site and reference the requirement for confined space permits. This ensures no space is overlooked during the planning stage.

5. Frequently Asked Questions

Does a deep manhole with an open top count as a confined space?▾

Yes, if a specified risk is present or foreseeable. The legal definition requires two criteria: the space must be substantially enclosed, and one or more specified risks must be present. A deep manhole is substantially enclosed even with an open top. If oxygen depletion, toxic gas accumulation, or any other specified risk could foreseeably arise, it is a confined space and requires a permit, atmospheric testing, a standby person, and rescue arrangements. The fact that it has an open top does not exempt it from the Regulations.

What training does the standby person need?▾

The standby person must be trained in the specific emergency procedure for the confined space, including how to raise the alarm, how to communicate with the entrant, how to initiate the rescue without entering the space, and how to operate any non-entry rescue equipment (e.g. retrieval winch). They must also understand, unequivocally, that they must never enter the space under any circumstances. Training should be documented and refreshed at appropriate intervals, typically annually.

Can mechanical ventilation remove the need for atmospheric testing?▾

No. Mechanical ventilation is a control measure, not a substitute for testing. The atmosphere must be tested before every entry regardless of whether ventilation is running. Ventilation may fail, may be insufficient to clear all pockets of contaminated air, or may not reach all areas within the space. Continuous atmospheric monitoring must be maintained throughout the entry in addition to the pre-entry test. A space with ventilation running is still a confined space and still requires a permit.

How often must the gas detector be calibrated?▾

The detector must be calibrated in accordance with the manufacturer’s instructions, typically every six months, and must be bump-tested with a known concentration of test gas before each use. The calibration date and instrument serial number must be recorded on the permit. A detector that has not been calibrated or bump-tested provides unreliable readings and must not be used. Personal gas monitors worn by entrants must also be calibrated and bump-tested to the same standard.

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