A confined space is not defined by size. It is any place that is substantially enclosed and where there is a reasonably foreseeable specified risk: fire or explosion, loss of consciousness from gas, fume, vapour or lack of oxygen, drowning from rising liquid, asphyxiation from a free-flowing solid, or loss of consciousness from heat. A large grain silo is a confined space. An open-topped pit can be one. A locked cupboard usually is not.
What the Confined Spaces Regulations 1997 actually forbid
Regulation 4 of the Confined Spaces Regulations 1997 says nobody shall enter a confined space to carry out work unless it is not reasonably practicable to achieve that purpose without entry. Entry is the last resort, and the first question is always whether the job can be done from outside: cameras, remote sampling, robotic cleaning, and designing the plant so routine work does not need entry.
Confined space entry: the safe system for working in confined spaces
Where entry cannot be avoided, regulation 4(2) requires a system of work that renders the work safe as regards the specified risks. In practice that is isolation of incoming services and materials, cleaning or purging, testing the atmosphere before and continuously during entry, ventilation, controlling ignition sources, a top man in communication with the entrant, defined entry duration, and equipment suitable for the atmosphere.
The confined space permit, and why it exists
A confined space entry permit is the document that proves every one of those steps was checked by a named person immediately before entry, and that the space is handed back at the end. It exists because the failures are ones that a checklist catches: the isolation that was assumed, the gas test taken an hour earlier, the second entrant nobody logged.
Rescue is the part that kills people: plan the confined space rescue team
Regulation 5 requires suitable and sufficient arrangements for rescue to have been made before anyone enters. Would-be rescuers who go in without breathing apparatus make up a large share of confined space deaths, and they are usually colleagues who went in on instinct. A rescue arrangement means trained rescuers, the right equipment on site, a tripod and winch where the access allows it, and a plan that does not depend on somebody entering unprotected.
Why is methane gas dangerous in confined spaces?
It is dangerous in two separate ways at once. It is flammable across a wide range in air, so a spark can ignite an accumulation. And because it displaces air, it reduces the oxygen concentration, so a space can asphyxiate an entrant well before it reaches a concentration that would explode. That is why atmospheric testing checks oxygen, flammability and toxicity rather than any one of them.
Medium risk confined space work, and what the tiering means
Industry classifies confined space work as low, medium or high risk according to the atmosphere, the access and the rescue difficulty, and training is provided against those tiers. The tiers are an industry convention rather than a legal classification, and a space does not become safe because somebody labelled it medium risk.
What is a confined space uk law recognises
The definition is 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. Two halves and both have to be true: enclosed, and carrying one of the five specified risks. That is why a small cupboard with the door open is not one and a large room filling with an inert gas is. The practical consequence is that the answer depends on the work as well as the place: a dry pit is not a confined space until somebody starts welding or running a petrol cutter in it, at which point fire, fume and oxygen depletion all become foreseeable. A sensible assessment therefore asks the question for the TASK rather than labelling the room once and for ever.
Confined space regs, and the order they set
The regulations are short and their order is stricter than most: first, no person shall enter or carry out work in a confined space where it is reasonably practicable to do the work WITHOUT entering. That is a genuine duty rather than a preference, and it is answered by remote tools, cameras, sampling from outside, emptying and cleaning in place, or redesigning the asset so a person never has to go in. Second, where entry is unavoidable, there must be a safe system of work. Third, and separately, there must be suitable and sufficient arrangements for the rescue of any person in the event of an emergency, in place BEFORE anybody enters. The third duty is independent of the second, which is the point most often missed: a perfect safe system with no rescue arrangement is still a breach, and the reason is that the majority of confined space deaths include somebody who went in to help.
Questions people ask about confined space
What is classed as a confined space?
A place that is substantially enclosed and where one or more specified risks are reasonably foreseeable: fire or explosion, loss of consciousness from gas, fume, vapour or lack of oxygen, drowning, asphyxiation from a free-flowing solid, or loss of consciousness from heat.
Is a permit required to enter a confined space?
The regulations require a safe system of work rather than a permit by name, but a written permit is the normal and expected way of showing that system was applied before entry.
Do rescue arrangements have to be in place before entry?
Yes. Regulation 5 requires suitable and sufficient arrangements for rescue to have been made before any person enters.
Is a manhole a confined space?
Usually yes, because a sewer or drainage chamber carries foreseeable risks of gas, oxygen deficiency and rising liquid. Each space still has to be assessed on its own facts.
What should a confined space risk assessment cover?
Whether entry can be avoided at all, and where it cannot, the specified risks and the safe system of work: isolation of services and materials, cleaning or purging, atmosphere testing before and during entry, ventilation, ignition control, a top man in communication and a defined entry duration, with rescue arrangements in place before anyone goes in.