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LACK OR EXCESS OF OXYGEN Lack of oxygen can occur, for example, in a laboratory environment where oxygen is driven out by other gases. It can also occur in lorries or freight containers as a result of the cargo reacting with oxygen inside the space. A normal oxygen level is 20.9%, with 19.5% the minimum working level. Anything below this level can quickly affect the functioning of the brain and reduce a person’s ability to respond to his or her environment. Oxygen levels below 16% puts employees at risk of unconsciousness or even death. Conversely, excess oxygen presents a serious threat to workers too. Excess oxygen can be caused by leaking equipment and levels over 23.5% increases the risk of fire, particularly in clothing.

POISONOUS GAS AND FUMES These can build up in sewers, manholes and in pits connected to the system, be leaked into trenches and pits in contaminated land and can enter tanks or vessels through connecting pipes. These gases can be identified using correctly specified atmospheric testing equipment. Consideration should be given to the possibility of gases trapped in residues and sludge, scale or animal waste which may not have been identified by initial atmospheric testing and may be disturbed and released by someone working in the confined space. Toxic gases, fumes and vapours may also contaminate the confined space from the outside, such as from nearby processes or vehicle exhaust fumes.

FLAMMABLE SUBSTANCES Flammable substances, which may be present in the confined space, can cause fire or explosion if ignited. These can be gases, fumes, vapours and dusts and may come from the confined space contents or from materials being used to clean the confined space which have a flammable liquid base or from propellant gases of aerosol sprays for example. Where there is a possibility of flammable substances being present in a confined space then suitable equipment, including electrical equipment, will have to be specified to eliminate risk of a spark or ignition source.

EXCESSIVE HEAT Excessive heat can cause heat stress, leading to heat stroke, unconsciousness and even death. The heat can come from a plant, such as boilers, or an oven that has not had sufficient cooling time before entry. It can also be caused by the use of steam cleaners or hot water high pressure jetting systems. Inadequate ventilation or the lack of chilled ventilation along with the confined space entrants wearing chemical protective suits, which impair natural body temperature control, can exacerbate the heat problems in confined spaces.


TRAINING Once the hazards and risks have been assessed, the development of a safe working system is essential. It is worth reminding anyone managing confined space working that the first consideration should be identifying a method of doing the work remotely, rather than entering the space.

One element of providing a safe working system that is often overlooked is providing employees with adequate training in confined space entry, which is absolutely crucial. Employers have a legal duty to ensure that a safe system of work is implemented and realistic training should be provided to those working in confined spaces. Specific training for work in confined

spaces will depend on an individual’s previous experience and the type of work they will be doing.

It is likely that training will need to cover the need to avoid entry to a confined space, understanding of the work to be undertaken, the necessary precautions, understanding safe systems of work and what to do in emergencies. Training should also take into account the practical use of safety features and equipment and involve demonstrations and practical exercises to help participants fully understand the training.

REDUCED PHYSICAL DIMENSIONS These can be hazardous simply because they can make the way in and out of a confined space difficult to negotiate and make movement inside restrictive. There is also the possibility of gases being trapped in low lying areas inside the confined space where ventilation may be difficult to achieve. The use of breathing apparatus and rescue stretchers and equipment becomes much more difficult in smaller areas and specifying the right equipment and having it to hand before the first entry is very important.

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