11th May, 2022

7 Hazards That Make Confined Spaces Dangerous Places

Confined spaces are dangerous places. Working in confined spaces is not something that can always be avoided, so you need to know the hazards to watch out for. In this post, find out the 7 main hazards associated with confined space work.

7 Hazards That Make Confined Spaces Dangerous Places header image

If your work takes you into a confined space, you must proceed with caution. Because even if no hidden hazards are lurking inside, in a confined space, your movement may be restricted. This can make escape difficult, and the consequences of hazards much more serious.

Before you can tackle the risks associated with confined spaces, you need to be able to identify when work is being carried out in confined spaces, and the hazards associated with the confined space.

What is a confined space?

A confined space is an enclosed area where there is a risk of death or dangerous injury from hazardous substances or dangerous conditions.

A confined space is a place that is substantially enclosed (though not always entirely), and where serious injury can occur from hazardous substances or conditions within the space or nearby.

Enclosures with limited openings such as drains, sewers, tanks and silos are confined spaces. These are often places that are not usually entered by people, but may need to be during maintenance work or inspections.

During construction work, some areas may become confined spaces due to the work being carried out, for example within trenches, unventilated rooms or building voids.

What are the main confined space hazards?

If confined space work cannot be avoided, you need to take extreme care. If you run into trouble within a confined space, the consequences can be fatal. Here are our top 7 confined space hazards.

1. Lack of Oxygen

Oxygen can be removed from the atmosphere within a confined space through naturally occurring reactions. A reaction between certain soils and the oxygen, or groundwater and chalk or limestone can produce carbon dioxide which displaces oxygen. Rust forming inside tanks can also create a lack of oxygen.

In 2014 three crew members died at Goole Docks after entering a cargo hold.

The investigation found that the oxygen levels within the compartment had been depleted, probably by the timber cargo, with levels of 5% - 6% recorded at the compartment deck.

2. Gases, Fumes and Vapours

Poisonous gases and fumes can build up within confined spaces, especially where there is a lack of ventilation.

Deadly gases can leak into the confined space, for example through a burst gas pipe or from contaminated land. Or they may be created from the work being carried out, such as welding, adhesives or paint fumes.

Without extraction or ventilation, these gases and fumes can create a toxic atmosphere within the confined space.

3. Flooding

Liquids can quickly flood the confined space, particularly in drainage or sewer work, trapping and potentially drowning those within.

And it's not just liquids you should worry about. Solids can also flood confined spaces, for example in trench collapses, with those within the trench at the risk of being trapped or buried.

Confined spaces can be small, so flooding can occur in a matter of seconds, leaving no time to escape.

4. Dust

Dust can build up within confined spaces, either naturally occurring or through the activity being carried out, e.g. drilling or grinding.

Excessive dust inhalation causes respiratory problems, and hazardous dust can be fatal.

Dust build-up can also increase fire/explosion risk, especially where there is a lack of ventilation.

5. Fire and Explosions

Flammable vapours, liquids, gases and dust within the confined space can all increase the risk of fire and explosions. The risk is increased further where any hot works or tools which can spark are used within the confined space.

Remember how lack of oxygen was number one on our list? Well, too much oxygen is also bad. Excessive oxygen levels increase the risk of fire and explosions.

6. Temperature

Strenuous construction work, hot works or naturally occurring hot conditions can lead to a dangerous increase in body temperature. This can quickly become a problem within confined spaces that are hard to escape from at the best of times.

Heat can rapidly rise due to the enclosed nature of a confined space. This can lead to heatstroke, exhaustion and collapse.

7. Access Restrictions

Confined spaces are also dangerous because they can be difficult to access. This makes escape difficult and also hinders any emergency rescue.

Once you are inside a confined space, there may not be a quick or easy way out. So it is important to know that work can be carried out safely before you enter, and emergency arrangements are in place.

inside a confined space

Controlling Confined Space Hazards

If you can’t avoid work within the confined space, you need to carry out a confined spaces risk assessment to identify the hazards decide what precautions are needed to control the risk.

Every year, people die or get seriously injured during confined space work. Unfortunately, many deaths in confined spaces are from people attempting to rescue others and being exposed to the same hazards.

It is not possible to know all the hazards off the top of your head. If you enter confined spaces without sampling the atmosphere correctly or testing what is, or can be there, you will get it wrong at some point and the consequences can be fatal.

Gerry McCulloch HSE Confined Spaces Case Studies (IOSH Liverpool 2017)

Controls you might think about include:

Confined space work is high risk, and you must follow a safe system of work developed through risk assessment, method statement, control measures and permits to work.

Everyone involved with confined space work needs to have the right training and instruction so they can carry out the work safely, and not put themselves or others at risk.

No person at work shall enter or carry out any work in or (other than as a result of an emergency) leave a confined space otherwise than in accordance with a system of work which, in relation to any relevant specified risks, renders that work safe and without risks to health.

A confined space permit to work is an extra level of control, as the work will need to be authorised and signed off to say that all the necessary controls are in place.


Remember, confined spaces are dangerous places. The Confined Spaces Regulations apply to all work within confined spaces and must be applied.

Need help preparing your safe systems of work? We have health and safety documents to help you. Download the confined space risk assessment template to plan the work, the confined space permit to work to control the work, and the confined space toolbox talk to raise awareness.

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This article was written by Emma at HASpod. Emma has over 10 years experience in health and safety and BSc (Hons) Construction Management. She is NEBOSH qualified and Tech IOSH.

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