Control measures (2)

The HSE advise that all mechanical and electrical equipment should be isolated if it could be operated inadvertently inside a confined space. If gas, fume or vapour could enter the confined space, physical isolation of pipework etc needs to be made and then checks carried out to ensure isolation is effective. Cleaning may also be necessary before work is carried out to ensure fumes do not develop from residues.

Non-sparking tools and specially protected lighting are essential where flammable or potentially explosive atmospheres are likely. In certain confined spaces (e.g. inside metal tanks) suitable precautions to prevent electric shock include use of extra low voltage equipment (typically less than 25 V) and, where necessary, residual current devices.

In certain circumstances breathing equipment may be necessary. The HSE stress that is dangerous to "sweeten the air" in a confined space with oxygen as this can greatly increase the risk of a fire or explosion.

An adequate communications system is needed to enable communication between people inside and outside the confined space and to summon help in an emergency. Someone should be stationed outside the confined space to communicate with anyone inside, raise the alarm quickly in an emergency and take charge of the rescue procedures. Extra thought must be given to how an emergency situation from inside the confined space can be communicated to those on the outside.

A great deal of thought should be given to emergency procedures and training carried out to ensure all are aware of their responsibilities. Issues to consider include the provision of rescue and resuscitation equipment, the capability and readiness of rescuers, shutdown procedures, first aid and communication procedures with local emergency services. The risks to rescue workers must also be managed.

Finally, a "permit-to-work" may be necessary. This ensures that a formal check is undertaken to make sure all the elements of a safe system of work are in place before people are allowed to enter or work in the confined space. It is also a means of communication between site management, supervisors, and those carrying out the hazardous work. Essential features of a permit-to-work, according to the HSE, are:

> Clear identification of who may authorise particular jobs (and any limits to their authority) and who is responsible for specifying the necessary precautions (e.g. isolation, air testing, emergency arrangements etc)

> Provision for ensuring that contractors engaged to carry out work are included

> Training and instruction in the issue of permits

> Monitoring and auditing to ensure that the system works as intended

The advice contained in this feature is based upon the revised (June 2002) HSE leaflet "Safe work in confined spaces". More detailed guidance is also available from the HSE in "Safe work in confined spaces - Confined Spaces Regulations 1997 - Approved Code of Practice, Regulations and Guidance" available from HSE Books