Accidents Confined Space - Before going any further, it is essential to point out that a confined space is not the same as a restricted space. A confined space may be limited in terms of the available space to move in, but it becomes ‘confined’ when access and egress is restricted. Restricted space can have easy and multiple access and egress points, though it may be confined in terms of the space available to perform a specific task.
It is also important to point out that it is far easier to remember why you should or shouldn’t do something when working in a confined space if you also understand how accidents in confined spaces occur. That way, the rules, together with the advice given, will make much better sense.
One of the best ways to understand how accidents can be caused when working in a confined space is to read the current legislation, both in general terms through the Health and Safety at Work etc. Act 1974 and the Confined Spaces Regulations 1997. The legislation provides information that is extremely useful in establishing best working practices when operating within a confined space. It should also be noted that it is the employer's responsibility to ensure that any confined space worker is fully aware of all aspects of the legislation that apply to their work and that they also have a complete grasp of any emergency protocols in place in the event of an emergency. A thorough risk assessment can prevent accidents from occurring. Emergency protocols should also be made known to anyone involved in supervising or overseeing anyone working in a confined space.
Heat can be an insidious killer. We may be aware that we are hot, but we may not fully know how that heat affects our mental capabilities. Once our senses and mental function become impaired, so do our logic and reasoning; we become mentally incapable of making decisions that could help protect our wellbeing. According to Cognitive Vitality, “Heat stress-induced impairments to cognitive and motor functions increase the risk for accidents,” and “Performance on simple tasks is relatively unaffected, while complex tasks that require sustained attention are more heavily impacted. Significant cognitive and motor performance impairments become apparent when the internal body temperature reaches 101.3oF (38.5oC).” Normal body temperature is between 36.1°C to 37.2°C, so we are only talking about a rise in core temperature of just over 1.3o for heat to adversely affect our wellbeing. Heat stroke – which occurs when a body core temperature reaches above 40°C – is often fatal without urgent attention.
When working in a confined space, there are three principal heat sources. One of the principal reasons heat generation is so dangerous in a confined space is its ability to rapidly increase the ambient temperature owing to poor ventilation. So first, the heat can come from the general environment, even down to something as simple as the weather being sunny if the confined space you are working in is exposed to the elements, such as an above-ground section of a pipeline, or a roof void. Second, the heat can be generated by the tools we use for the required task. Grinding and welding are two heat-generating tasks that generate considerable heat. Third, and the source that is most frequently overlooked, is us, and our colleagues. This is a dual problem as while we, as an individual, can increase the temperature of a confined workspace over a reasonable period of time, a group of four or five people working in a confined space can substantially increase the temperature remarkably rapidly.
One of the major problems with confined spaces is a lack of good ventilation. Without good ventilation, there is no replenishment of supplies of oxygen, and instead, the air can become contaminated with noxious fumes given off, e.g., by materials stored in confined spaces such as petrochemicals, solvents, animal waste and food waste. In addition, while not exactly toxic gases, the formation of rust in confined spaces where there is next-to-no ventilation can create a significant risk as the chemical reaction which creates rust removes oxygen from the air.
Noxious fumes can cause immense harm to our ability to breathe and function through multiple effects. While the fumes, per se, may not always be poisonous to our system, they can displace oxygen, affecting our ability to breathe successfully and causing oxygen starvation. A self contained breathing apparatus is vital when working in such conditions.
One of the other problems with harmful gases in confined spaces is that they are invisible. Unlike smoke or fumes, you physically cannot see such toxic gases as methane, carbon monoxide, hydrogen sulphide and nitrogen oxides. At the entrance to a confined space, there may be sufficient air circulation for the levels of a poisonous gas not to be harmful. However, as you move further into the confined space, the less the poisonous gases have been replaced by freshly circulating air. Additionally, while some poisonous gases are easily detected through their smell, if you are wearing a full-face mask or respirator, you won’t be aware of their presence. Thus you may be protected against poisoning from the gases present, but if you are unaware of their existence, the risk of causing an explosion increases.
As we have identified above, gases can build up over time in confined spaces, and some of these gases are flammable, such as methane. One area of confined space where methane was responsible for countless deaths was down coal mines, where ventilation was always a problem, and a build-up of methane gas was a perpetual risk, which lead to frequent explosions.
For an explosion to occur in a confined space, or in any space, you need three elements, which are:
While it can come in the form of a solid, frequently, it is the presence of gas or dust particles that provide the fuel element necessary for an explosion. Where oxygen is concerned, nothing can burn without its presence. For this reason, in confined spaces where the environment may make breathing more complex, it is highly dangerous to pump in a supply of pure oxygen to assist.
Ignition can come in many forms, but it is essential to understand that not all of them may be wholly obvious. Any form of spark has the potential to act as a point of ignition for an explosion. This can be created by tools being used, so the choice of tools is critical in certain circumstances. “Non-sparking”, “spark reduced”, “spark-resistant” or “spark-proof” tools are names given to tools made of metals such as brass, bronze, Monel metal (copper-nickel alloy), copper-aluminium alloys (aluminium bronze), or copper-beryllium alloys (beryllium bronze) which eliminate the possibility of creating sparks.
However, there is one source of an ignition spark that is frequently overlooked, and that is one created by static electricity. This can often be caused by nylon workwear, so extra care should be taken when choosing appropriate PPE.
It is worth noting that the risk of an explosion at work is a significant risk factor, and consequently, the UK Health and Safety Executive has issued specific regulations to minimise the risks with the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).
While it is easy to concentrate on explosions caused by flammable gases, this can distract from another main cause of explosions, and that is dust. Because we associate dust as being made up of solid particles as opposed to lighter gases, we tend to ignore the fact that dust can be equally as flammable as some gases, and even more so. Combustible dust, also known as explosive dust, is often invisible to the naked eye, so it is vital to understand the environment you are working in. Dust explosions result from high concentrations of combustible dust particles rapidly combusting inside an enclosed space. When mixed with oxygen, these minute particles can easily ignite by a spark or other ignition source. This rapid combustion process is known as deflagration and results in a high-pressure airwave.
As the airwave explodes out of its enclosed space, it will likely stir up combustible dust elsewhere nearby. This then creates a further airborne mix of dust which, with the oxygen in the air, will make the initial explosion bigger, and potentially create a second dust explosion – or even a chain of explosions.
Now that you have a better understanding of the causes of accidents in confined workspaces, we would recommend you also read our article 10 ways to reduce the chances of having an accident when working in a confined space. After all, it is said that prevention is better than cure, and it is fair to say that you can never pay too much attention to reducing the risk of an accident in a confined workspace.
Here at Commodious we specialise in providing online courses that cover many aspects of Health & Safety. If you would like to learn more about any of these, please feel free to get in contact with us.