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Confined Space

Confined Spaces - How To Make Sure You're Working Safely - Part 1

In this two-part guide, we're going to look at the risks and safety procedures involved when we're working in confined spaces.

This is Part 1 and we'll be defining what a confined space is, what atmospheric hazards are, and factors involved in atmospheric testing.

Part 2 of our guide will cover how to monitor in confined spaces and the safety products that are best suited for when working in such spaces.

What is a Confined Space?

For many, working within a confined space is a daily requirement. Such a space is defined as:

  • being large enough for an employee to enter and perform work
  • having limited or restricted means for entry and exit
  • not being designed for continuous human occupancy

So, storage tanks or vessels would fall into the category of confined working space. As would agricultural silos, marine vessel tanks, sewers or manholes.

In the UK there are clear government outlines regarding what is classed as a confined space - and the proper working requirements therein - and these can be found here.

Atmospheric Hazards in Confined Spaces

working safely in a confined space
confined space atmospheric hazards

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Due to the very nature of confined spaces, there are atmospheric hazards that need to be factored into creating a safety plan for anyone working in them. Being aware of the risks, whether entrapment, injury or acute illness, is the first step in making sure we're working safely in the confined space.

The atmospheric risks include the following:

  • oxygen. Whether this is because of enrichment or deficiency, being aware of the oxygen levels within the confined space is paramount. Too much oxygen in the atmosphere presents the risk of fire, while too little oxygen will result in impaired coordination, respiratory impairments, and even death

As a result, testing the quality of the air within the confined space, both before entry and while working, is critical. In Part 2 of this guide we'll look at some key pieces of equipment that will enable this.

  • combustible gases. Any flammable gas or vapour that exceeds 10% of its "lower explosive limit" - or LEL - is a risk. That's because these gases are too lean to burn. Alternatively, if the flammable gas is above its "upper explosive limit" - or UEL - the mixture will be too rich to burn. For example, oxygen content in the air of between 8% and 10% will result in fainting, mental failure and unconsciousness. Whereas oxygen content exceeding 23.5% presents an extreme fire risk

monitoring confined spaces for safe workingAs combustion of gases present in a confined workspace is a clear risk, it's important to understand how combustion occurs. For this to happen there's needs to be four elements, as illustrated by the "fire tetrahedron":

  1. 1. fuel
  2. 2. oxygen to support combustion
  3. 3. heat or a source of ignition
  4. 4. chain reaction

The chain reaction component of the fire tetrahedron refers to the fact that the first 3 components must be present in such proportions to allow a flame to propagate.

Again, testing the atmospheric conditions within the confined workspace is the first step to preventing this chain reaction occurring. Equally, testing for the presence of hazardous gases such as ammonia, chlorine, nitric oxide, etc is a firm requirement of safely working in a confined space.

Monitoring Confined Spaces for Atmospheric Hazards

Prior to entering a confined space, the air must be monitored. What you're looking for includes:

  • the proper levels of oxygen
  • no combustible gases are present
  • toxic gases are below the permissible working limits

When monitoring you need to take samples of the air at the top, middle and bottom of the confined space as the gases and vapours will vary in concentration. Depending on the density of the gas, you may find highly concentrated levels at the top or very bottom of the workspace. And you must sample the air at a distance from the opening to the confined space. That's because the air from outside will give you a false sense of adequate oxygen presence.

To carry out these atmospheric tests requires the equipment that's properly calibrated for the job. In Part 2 of this guide, we'll list some of the best monitors available to make sure you - and your team - are always safe when working in confined spaces.

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Disclaimer:

Under no circumstances should a confined space be entered or monitoring equipment used except by qualified and trained personnel, and after all instructions have been carefully read and understood and all precautions followed. This article only a general description of atmospheric testing in a confined space and equipment used to monitor a confined space.