In any confined workspace, restricted ventilation will cause the build up of a potentially hazardous atmosphere.
An example of confined spaces would be a storage tank. It may also contain, or have contained, toxic, flammable or hazardous substance, vapour or gas.
It is clear that working in such spaces requires a greater than normal awareness of potential hazards and increased attention to safe working practices.
Welders working in enclosed spaces must be properly trained, equipped and supervised.
Additional protective and monitoring equipment (over and above that normally necessary) may be required when welding in a confined space.
It is recommended that a formal 'safe system of work' should be followed at all times.