Confined space regulations: what a confined space is and what the law requires

A confined space is a place that is substantially enclosed and where a "specified risk" is reasonably foreseeable: serious injury from fire or explosion, loss of consciousness from a rise in body temperature, loss of consciousness or asphyxiation from gas, fume, vapour or lack of oxygen, drowning, or asphyxiation by a free-flowing solid such as grain. That is the definition in regulation 1(2) of the Confined Spaces Regulations 1997. In England, Wales and Scotland they require you to avoid entry where you can, follow a safe system of work where you cannot, and have rescue arrangements ready before anyone goes in.

Northern Ireland has its own regulations, S.R. 1999/13, with the same definition.

What is a confined space?

Regulation 1(2) of the Confined Spaces Regulations 1997 defines it:

"confined space" means any place, including any chamber, tank, vat, silo, pit, trench, pipe, sewer, flue, well or other similar space in which, by virtue of its enclosed nature, there arises a reasonably foreseeable specified risk

HSE's Approved Code of Practice and guidance, L101, reads that as two tests. The space must be substantially, though not always entirely, enclosed, and one or more of the specified risks must be present or reasonably foreseeable. Regulation 1(2) of the Confined Spaces Regulations 1997 lists the risks:

Specified risk	How L101 says it arises
Serious injury from fire or explosion	Fumes left in a tanker that carried petrol, oxygen leaking from welding equipment, airborne flour dust
Loss of consciousness from a rise in body temperature	Boilers entered before they have cooled, hot work, strenuous work in protective equipment
Loss of consciousness or asphyxiation from gas, fume, vapour or lack of oxygen	Sewer and slurry gases, residues disturbed by cleaning, rust forming inside a closed steel vessel, welding fume
Drowning from a rise in the level of a liquid	Water surging into a sewer, liquid entering from plant that has not been isolated
Asphyxiation by a free-flowing solid, or entrapment in one	Grain, sugar, flour or sand, which can submerge a person

L101's examples show a confined space can be open-topped, like a vat, very large, like a grain silo, and somewhere people use regularly for their work, like the spaces used for spray painting in car repair centres.

The work itself can create one. Welding uses up oxygen and chemical cleaners give off fumes, so a space can be a confined space while the job runs and stop being one once the fumes are ventilated and the air tested. Storage can do the same: L101's examples include carbon dioxide or argon cylinders held in an enclosed space. Once a space meets the definition, the Regulations apply in full, even where the specified risk is controlled.

An enclosed space with no specified risk falls outside the Regulations. L101's examples are ceiling voids, lofts and some cellars, which have their own risks to assess.

Examples from the sectors we work in

L101 adds ducts, manholes, sumps, under-machine pits, freight containers and plant rooms to the regulation's list. Each still has to meet both tests.

Place	Sector	What makes it a confined space
Underground fuel tanks	Petrol forecourts	A tank, with petrol vapour giving a risk of fire or explosion
Oil separators, also called interceptors	Petrol forecourts	A chamber that traps petrol and oil, so flammable vapour can collect inside, and more is released when sludge is disturbed
Sewers, manholes and drainage chambers	Any site with drainage	Toxic gas and methane, lack of oxygen, water surging in after heavy rain
Silos and hoppers of grain, flour, sugar or sand	Manufacturing	Engulfment, material that "bridges" and then collapses, and dust explosion where the material is grain, flour or sugar
Enclosed stores of steel chain, swarf or scrap, and steel vessels left closed	Metal stockholding	Lack of oxygen, used up as the steel rusts
Freight containers	Warehousing and logistics	Lack of oxygen where the cargo reacts with the air, fumigant left inside
Cellars holding carbon dioxide or mixed gas cylinders for drinks dispense	Hospitality	Asphyxiation from a leak, because carbon dioxide is heavier than air

On a forecourt in Great Britain, the petrol vapour that makes a tank a confined space is also why the tank area is classified into hazardous zones under regulation 7 of the Dangerous Substances and Explosive Atmospheres Regulations 2002. A DSEAR risk assessment covers the zoning, and entering the tank or interceptor needs its own confined space assessment and safe system of work.

What do the Confined Spaces Regulations require?

Regulation 3 of the Confined Spaces Regulations 1997 puts the duties on employers and the self-employed. An employer must make sure the Regulations are complied with for work done by its own employees, and so far as is reasonably practicable for others, such as contractors, in matters within its control. HSE sums up the rest as three duties.

Avoid entry where you can

Regulation 4(1) of the Confined Spaces Regulations 1997 is a prohibition: "No person at work shall enter a confined space to carry out work for any purpose unless it is not reasonably practicable to achieve that purpose without such entry." So the first question for every job is whether it can be done from outside. L101's examples include:

• testing the atmosphere or sampling the contents with long probes
• cleaning with water jetting, steam or long-handled tools
• clearing silo blockages with remotely operated flails, vibrators or air purgers
• inspecting through a sight glass or with CCTV

Follow a safe system of work when entry is unavoidable

Regulation 4(2) of the Confined Spaces Regulations 1997 requires anyone who enters, works in or, other than in an emergency, leaves a confined space to do so, so far as is reasonably practicable, under a system of work that "renders that work safe and without risks to health". L101 says the system should be in writing, and is specific on four points:

• Test the air before entry: oxygen first, then flammable gas, then toxic gases, vapours and dusts. Normal oxygen is 20.9%, and below 16% can lead to unconsciousness and death.
• Never add oxygen to "sweeten" the air. Enrichment can make grease liable to spontaneous combustion and other materials far more combustible.
• Purge flammable gas or vapour with inert gas only, because purging with air could create a flammable mixture.
• Keep petrol-fuelled engines out of confined spaces altogether.

Have rescue arrangements ready before anyone goes in

Regulation 5(1) of the Confined Spaces Regulations 1997 bars anyone at work from entering or working in a confined space until "suitable and sufficient arrangements for the rescue of persons in the event of an emergency" have been prepared, "whether or not arising out of a specified risk". Under regulation 5(2) of the Confined Spaces Regulations 1997, the arrangements must reduce the risks to rescuers so far as is reasonably practicable, and must provide and maintain resuscitation equipment where resuscitation is a likely consequence of a specified risk.

L101 says a major cause of death and injury in confined space incidents is "ill-conceived attempts to save others who have collapsed or ceased to respond". It says you should not rely on the public emergency services, and that rescue equipment will often include lifting equipment, because "even a strong person is unlikely to be able to lift or handle an unconscious person on their own using only a rope".

How do you carry out a confined space risk assessment?

Regulation 3 of the Management of Health and Safety at Work Regulations 1999 requires a suitable and sufficient assessment of the risks. L101 says it should identify which spaces are confined spaces, and its first priority is a way to avoid entry. Where entry is unavoidable, the assessment must be carried out by someone competent, with the skills, knowledge and experience of the processes, plant and equipment to understand the risks and devise the precautions. Spaces that are broadly the same, such as manholes, can share a model assessment that picks up any differences.

The assessment should cover:

• what the space held before, residues, contamination from nearby plant or the ground, and the oxygen level
• its size and layout, including low-lying pockets where the air can differ
• what the work brings in, such as cleaning chemicals, ignition sources and heat
• what could get in from outside: liquids, gases, steam, engine exhaust, or machinery starting up
• who will go in, including their experience, their build where the space is tight, and conditions such as claustrophobia or asthma
• how you would get someone out

On previous contents, L101 records fires and explosions caused by substances "thought to have been 'removed' some considerable time before, but which were, in fact, still present". If you employ five or more people, regulation 3(6) of the Management of Health and Safety at Work Regulations 1999 requires you to record the significant findings.

When do you need a permit to work?

L101 says a permit-to-work system is usually required where there is a reasonably foreseeable risk of serious injury in entering or working in the space. The permit extends the safe system of work and records the authorisations, the gas test results and any time limit on entry. It makes nothing safe on its own, and is cancelled when the job finishes.

L101's example of a job unlikely to need one meets three conditions together: easily controlled risks, a very simple system of work, and no other work that could affect the space. A competent person should take that decision. Our one-day permit to work course is for the supervisors and managers who issue and sign off permits, confined space entry permits included.

What training do you need to work in a confined space?

L101 says workers "must have adequate training and experience in the particular work involved to be competent to work safely in a confined space". Regulation 13 of the Management of Health and Safety at Work Regulations 1999 requires adequate health and safety training when people are exposed to new or increased risks.

L101 says the training needs to cover the Regulations and the duty to avoid entry, the work with its hazards and precautions, safe systems of work including permits, and how emergencies arise. L101 also sets out what each role involves:

Role	What L101 says
Supervisors	Running the permit system, checking the precautions are taken, and staying present where the risk assessment calls for it
People who go in	Practical exercises with the gas monitors, breathing apparatus, escape sets and communication methods they will rely on, and refreshers based on how long since they last did the work
People who test the air	Competence in testing, interpreting the results and acting on them, with records kept
Rescuers	Rescue training, with refreshers such as annually and realistic practice that can include a full-weight dummy. Regulated rescue qualifications exist

Our one-day Confined Space Awareness course is for staff, supervisors and managers on sites with confined spaces. It covers the Confined Spaces Regulations 1997 and the Approved Code of Practice, identifying and controlling the risks, safe systems of work and permits to work, and emergency procedures. We run it on your site for up to eight delegates, built around your own spaces and permit system. It is an awareness course and does not qualify anyone to enter: entrants need entry training for the space and equipment, and rescuers need rescue training.

Is there a 2021 update to the confined space regulations?

No. Only two instruments on legislation.gov.uk carry "confined spaces" in their title, and the 1997 Regulations have been amended by one instrument, in 1998:

Document	Where it stands, checked 2 November 2026
Confined Spaces Regulations 1997, S.I. 1997/1713	The law in England, Wales and Scotland, in force since 28 January 1998. The Diving at Work Regulations 1997 (S.I. 1997/2776), its one amending instrument, replaced the diving definition in regulation 1(2) of the Confined Spaces Regulations 1997 and the diving exemption in regulation 2(c) of the Confined Spaces Regulations 1997, from 1 April 1998
Confined Spaces Regulations (Northern Ireland), S.R. 1999/13	The law in Northern Ireland, made 14 January 1999, with the same definition
L101, Safe work in confined spaces	HSE's Approved Code of Practice and guidance, third edition, in effect from 19 December 2014

The Code has a special legal status. In L101's words: "If you are prosecuted for breach of health and safety law, and it is proved that you did not follow the relevant provisions of the Code, you will need to show that you have complied with the law in some other way or a court will find you at fault."

Frequently asked questions

What is classed as a confined space? Any place that is substantially enclosed and where one of the specified risks in regulation 1(2) of the Confined Spaces Regulations 1997 is reasonably foreseeable. The regulation itself names tanks, silos, sewers, pits and vats among its examples.

What are the confined space regulations? In England, Wales and Scotland, the Confined Spaces Regulations 1997: avoid entry where the work can reasonably be done another way, use a safe system of work when entry is necessary, and have rescue arrangements ready first.

Is a confined space risk assessment a legal requirement? Yes. In England, Wales and Scotland, regulation 3 of the Management of Health and Safety at Work Regulations 1999 requires a suitable and sufficient risk assessment, and L101 says someone competent must carry it out.

Do you need training to work in a confined space? Yes. L101 requires adequate training and experience in the particular work, and rescuers need training for their role.

Is there a confined space regulations 2021? No. The law in England, Wales and Scotland is still the Confined Spaces Regulations 1997, amended only in 1998, with the third edition of L101 from 2014.

Do you need a permit to work for a confined space? Usually. L101 says one is usually required where there is a reasonably foreseeable risk of serious injury.

Can you rely on the fire and rescue service to get someone out? No. L101 says you should not rely on the public emergency services, and in England, Wales and Scotland regulation 5 of the Confined Spaces Regulations 1997 requires your own rescue arrangements first.

Is a loft or cellar a confined space? Only if it is substantially enclosed and one of the specified risks is present or reasonably foreseeable. A cellar holding carbon dioxide cylinders is one to check.

Where to start

Walk each site with the list in regulation 1(2) of the Confined Spaces Regulations 1997, and L101's additions to it, to hand, and list every tank, pit, chamber, silo, duct and container that could meet both tests. For each one, ask first whether the job can be done from outside. Where it cannot, the risk assessment, the written safe system of work and the rescue arrangements come before entry.

Before the awareness course, we review the confined spaces and permit arrangements on your site, so delegates learn the spaces, hazards and controls on their own site.