Alternating current (AC) and direct current (DC) have slightly different effects on the human body, but both are dangerous above a certain voltage. The risk of injury changes according to the frequency of the AC, and it is common for DC to have an AC component (called ripple). Someone with special equipment can measure this, but the effect on a particular person is very difficult to predict as it depends upon a large number of factors. As a consequence you should always avoid contact with high-voltage electrical conductors, regardless of the type of electrical current they are carrying.

More detailed technical information on electrical injury is given in the standard BS PD 6519 ‘Guide to the effects of current on human beings and livestock – Part 1: General aspects’ see: British Standards Institution link to external website[1] (BSI) for more information.

No, not if they are careful and follow the simple rules to securely isolate electrical equipment, and check it is dead before they start work. If you received an electric shock but were not injured then you were lucky. Next time a slight change in events may lead to a very different result. No-one is immune to injury from electricity.

For more information, see:

The best way to find out if your electrical installation is safe is to have it inspected and tested by a person who has the competence to do so, such as an approved contractor from:

Approved electrical contractors from these bodies will be able to advise you how to make your installation safe. These can be found in the Yellow Pages.

It is possible to do simple checks on your installation, using an electrical socket tester. This is a device that can be plugged into a socket outlet to identify if there is a wiring fault. However, be aware that many types of socket tester can’t detect certain types of fault, and could indicate the socket is safe when it actually isn’t. For further information on socket testers, see the Electrical Safety Council’s Best Practice Guide PDF link to external website[14].

If you think you have an unsafe electrical installation you should first warn everyone to stay away from it and – if safe to do so – switch it off. You should then contact a competent person, such as an approved contractor from:

If the installation you think is unsafe is not owned by you or under your control, you should try to find out who owns it and then contact them. Electrical distribution poles, pylons and equipment should have a contact telephone number attached to them.

If you can’t find out who owns or controls an electrical installation that you think is unsafe, you should contact your local authority or HSE[21].

A wide range of voltages can be dangerous for different reasons. A very low voltage (such as that produced by a single torch battery) can produce a spark powerful enough to ignite an explosive atmosphere. Batteries (such as those in motor vehicles) can also overheat or explode if they are shorted.

If a person comes into contact with a voltage above about 50 volts AC, they can receive a range of injuries, including those directly resulting from electrical shock (problems with breathing, heart function etc); and indirect effects resulting from loss of control (such as falling from height or coming into contact with moving machinery). The chance of being injured by an electric shock increases where it is damp or where there is a lot of metalwork.

Electrical or thermal burns can also occur from the flow of electrical current or hot surfaces, see: Electrical injuries[16].

Electrical equipment should be visually checked[46] to spot early signs of damage or deterioration. Equipment should be more thoroughly tested by a competent person often enough that there is little chance the equipment will become dangerous between tests. Equipment used in a harsh environment should be tested more frequently than equipment that is less likely to become damaged or unsafe.

It is good practice to make a decision on how often each piece of equipment should be checked, write this down, make sure checks are carried out accordingly and write down the results. You should change how often you carry out checks, according to the number and severity of faults found.

For more information, see: Electrical safety and you: A brief guide,[47] or the detailed guidance in: Resources[48]. See also: FAQs on portable appliance testing[49].

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