The levels of oxygen in confined spaces can be depleted when there is reaction between some soils and oxygen in the atmosphere; or release of gas such as carbon dioxide that can displace ambient air. Poisonous gases, fumes or vapours can built up in the sewer; enter from connecting pipes; or leak from other areas. Residues left on surface of walls can give off gas, fume, or vapour. Scraping before painting can give rise to particulates that can contaminate the ambient air. Spray painting can give rise to volatile organic compounds depending on the composition of the paint. Volatile organic compounds can have adverse health effects including cancer. The person conducting the operation is at major risk for adverse effects described above. Since the sewer is located below a field where cattle and sheep graze, an open sewer could be a fall hazard for these animals.
The control system for this operation includes barricades and procedures for confined space work. According to the Management of Health and Safety at Work Regulations 1999 hazards must be identified; risks assessed and precautions determined. According to the Confined Spaces Regulations 1997 presence of risks of serious injury as in the operation requires following a safe system of work, and putting in place adequate emergency measures before the start of work. The safe system of work is based on the operation described above. A supervisor should be given responsibility for ensuring that necessary precautions are observed for checking the safety at each stage and being present when the work is in execution. The operator must have sufficient experience in conducting painting work in confined spaces. A determination has to be made if there is the need to isolate the sewer, and it must be checked if the isolation is effective. Before entry cleaning is required to determine whether fumes do not develop from residues while work is