The main electrical hazards are from contact with live parts, arcing, fires and explosion. Risk of injury is higher when the working environment is wet, outdoors or cramped. Underground cables are a problem for construction workers - for example pneumatic drilling into the ground. Overhead power cables are also a major hazard - for example workers can be electrocuted when machinery, scaffold poles or glazing rods come into contact with them.

The passage of electric current through the body may cause muscular contractions, respiratory failure, fibrillation of the heart, cardiac arrest or injury from burns.

Non-fatal shocks can cause severe or permanent injury. Shocks from electrical installations or equipment may lead to falls from heights. Electrical workers are not the only workers at risk; any worker using poorly installed or faulty appliances is at risk from shocks or fires.

Regulation 12(8) of the Construction (Health, Safety and Welfare) Regulations 1996 states: 'No excavation work shall be carried out unless suitable and sufficient steps have been taken to identify and, so far as is reasonably practicable, prevent any risk of injury arising from any underground cable or other underground service.' Anyone who is in charge of construction work has a duty to ensure this regulation is adhered to; a cable avoidance tool (CAT) scan will discover the presence of underground electrical cables. [See the case study below]

The Electricity at Work Regulations 1989 require precautions to be taken against the risk of death or injury from electricity during work at or near electrical systems. This includes both electrical installations and electrical equipment.

The legislation affects the construction industry in the following ways:

Electricians and engineers must remain safe when working on electrical systems.
Work done on electrical systems must be properly carried out and safe for other people.
Construction workers must remain safe when working in proximity to electrical systems.
All electric tools and equipment used by construction workers must be safe to use.
Any electric tools hired out to end-users must be safe to use.
The risk of injury from electricity is strongly linked to where and how it is used with the greatest risks being when working in harsh conditions:

Wet work - unsuitable equipment can easily become live and can make its surroundings live;
Outdoors - equipment may not only become wet but may be at greater risk of damage;
Cramped spaces - with a lot of earthed metalwork, such as inside a tank or bin - if an electrical fault developed it could be very difficult to avoid a shock.
There are many ways to reduce the risks when working with electricity. Measures suggested by HSE in Electrical safety and you include:

Ensuring an electrical installation is safe: By making sure new installations adhere to BS 7671, maintaining existing installations and providing enough socket outlets.
Providing safe and suitable equipment: For example, by choosing suitable equipment for the job, by using alternative devices where possible such as air tools, providing clearly identifiable switches to isolate machines, and protecting easily broken fittings such as light bulbs.
Reducing the voltage: By using battery operated tools, lower voltage temporary lighting and running power tools on lower voltages.
Providing a safety device: By running a Residual Current Device which detects some, but not all, faults in an electrical systems and turns the supply off.
Carrying out preventive maintenance.
HSE says employers must ensure people working with electricity are competent to do thejob and toensure :

Suspect or faulty equipment is taken out of use, labelled 'DO NOT USE' and kept secure until examined by a competent person;
where possible, tools and power socket outlets are switched off before plugging in or unplugging;
equipment is switched off and/or unplugged before cleaning or making adjustments;
equipment repairs or alterations to an electrical installation are only tackled by people with a knowledge of the risks and the precautions needed;
work on or near live or exposed parts of equipment is only allowed if it is absolutely unavoidable and the necessary precautions have been taken.
According to the HSE, 25 per cent of all reportable electrical accidents involve portable appliances. Portable appliance testing (PAT) is an important part of complying with electrical health and safety legislation. Regular PAT testing should be done where electrical equipment is used by employees or is hired out.

Case study

The Health and Safety Executive (HSE) issued a warning to the construction industry to ensure safe working practices are followed when working near buried electrical cables.

The warning followed the successful prosecution of Octain Construction Ltd, which was fined £10,000 plus £5,000 costs at the Old Bailey on 14 January 2001, following an accident to an employee in February 2000.

Mr Tomor Mucolli, a seventeen year old labourer, was using a pneumatic breaker to excavate a post-hole when he struck a live 11kV electric cable. He suffered severe burns to his face, arms and neck.

Octain pleaded not guilty to breaching Section 2(1) of the Health and Safety at Work etc Act 1974 (the HSW Act) that the company failed to ensure the safety of employees. Octain also pleaded not guilty to breaching the Construction (Health, Safety & Welfare) Regulations 1996 that the company allowed work to be carried out without suitable and sufficient steps being taken to prevent any risk of injury.

HSE investigating inspector Peter Lennon, said:

"This was a preventable accident. Work near underground services, including live electrical cables, is a hazardous activity. Although the company had assessed the risks and drawn up a method statement for carrying out the job, they failed to follow it.

"This case highlights the need for all those involved in working near underground services, including live electrical cables, to ensure that a safe system of work is followed. Such a system includes using hand, rather than power tools, scanning the area for services using a cable detector, marking the location of cables and ensuring the work is properly supervised. As work continues, repeat scanning should be carried out.