Safe Working in Confined Spaces: A Coffee Break Primer

23rd March 2021

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Safe Working in Confined Spaces: A Coffee Break Primer

Death and serious injuries continue to occur in the UK among those who work in confined spaces. That’s why it’s important to regularly remind both experienced professionals and newcomers to the subject of the essentials.

In a number of industries, from complex facilities to simple storage vessels, harm can not only come to those working directly on a task but to those who try to rescue them without proper training and equipment. A Marine Accident Investigation Branch safety warning issued after one such incident on a general cargo vessel can be found here.

We’ll overview the dangers of confined spaces, explain the particular risk from hazardous atmospheres and – most of all – outline some vital key rules every workplace should keep to the fore at all times.


What is a Confined Space?

A confined space is defined by the UK Health and Safety Executive as: “a place which is substantially enclosed (though not always entirely), and where serious injury can occur from hazardous substances or conditions within the space or nearby (e.g. lack of oxygen)”.

Some examples of confined spaces? The obvious instances include work on storage tanks, void space, boilers and drains however open-topped chambers, ductwork and even poorly or unventilated rooms can present a risk.

The HSE also details some relevant legislation, however our aim here is a brief overview of the risks and some vital accident prevention methods. This blog should not be used as a single source of advice before starting or preparing for an on-site as the correct risk assessment, legislative knowledge etc should be in place before any confined space work is carried out.


Why are Confined Spaces Dangerous?

It’s simple: a lack of oxygen can have very serious consequences in a short period of time.

However, this reduction in oxygen can happen for more reasons than might be immediately apparent.

Dangerously low levels of oxygen can occur for reasons including a reaction between some soils and oxygen in the atmosphere or in a ship’s hold or in storage or vehicles due to cargo reacting with oxygen inside the space. Steel tanks and vessels where rust has formed are also a risk.

Meanwhile, poisonous gases, fumes or vapour can be present due to a build-up in pipes, pits etc connected to the system, leak into the work area due to contaminated land or be present due to residue left in a tank.

A risk from high levels of dust or from dangerously hot conditions can also exist in confined spaces.

What are Hazardous Atmospheres?

A lack of natural air movement in a confined space can be extremely dangerous and lead to:

• Oxygen deficiency in the atmosphere: Because an oxygen-deficient atmosphere is considered to be one with less than 19.5% available oxygen, atmosphere with less than 20.8% oxygen should not be entered!

• Flammable atmospheres: This can happen due to the oxygen in the air or a flammable gas, vapour or dust in the proper mixture. Different gases have different flammable ranges. If a source of ignition is introduced into a confined space containing a flammable atmosphere, an explosion will result.

• Toxic atmospheres: Ranging from fast-acting poisons to long-term cancerous carcinogens, toxic atmospheres can – as mentioned above – be present due to product stored in a space (even after the product has been removed due to be absorbed or remaining as residue).

These dangers are especially relevant to work such as welding cutting, brazing, painting, scraping and sand blasting etc being carried out in a confined space.

Particular attention should be paid to vapours from, for example, cleaning solvents. Note that the toxicants can enter nearby confined spaces as well as the immediate work area.

Find out more about air flow and gas detection here.

Ventilation: The Key Rules

Efficient ventilation has three simple jobs: to provide sufficient airflow, reach the entire confined space and avoid introducing polluted air inside the confined space.

To provide sufficient airflow:

• It is recommended to have a ventilator that is able to ventilate 20 times the volume of the confined space per hour.

• It is recommended to ventilate 7.5 times the volume of the confined space before entering.

Note: the bigger the airflow of the device, the less time is needed to “secure” the confined space before entering in it.


To reach the entire confined space It is generally more effective to ventilate a confined space by pushing fresh air into it than extracting:

• The pushed air is going 30 times further than if it was exhausted.

• You are creating a real air stream inside the whole confined space. If you are exhausting there are some places in the confined space where the polluted air could remain.

To avoid introducing polluted air inside the confined space it is important to be sure that the air pushed inside the confined space is not polluted.

The ventilator should therefore not be placed very close to the confined space, as it could simply push the polluted air back into the confined space.

Equipment for Safer Confined Spaces Working

We’re much more than just an equipment ‘supplier’. We actively help our clients safely achieve optimal ventilation, heat and lighting results in challenging environments using stand-alone solutions often purpose-made for confined spaces. Our in-house product development team can even devise a bespoke solution.

After all, we bring almost 100 years of pacesetting service and knowledge - with a foundation in the most extreme shipping and oil industry environments – to global clients across aerospace, shipping, defence, utilities, pharmaceuticals, distilling, power stations and more.

This means SA Equip portable air, light, heat and power products have been proven in challenging conditions offshore, in the air and beyond for almost a century.

Contact us

For help with choosing the right equipment or to find out more about our bespoke equipment service.