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High Intensity Discharge Lighting [Hardfacts]


High Intensity Discharge Lighting (HID) is widely used in commercial and industrial facilities to provide an efficient, low cost light source. These lights operate at a high internal pressure and temperature (up to 6 bar and 1,300OC) and so catastrophic failure is possible. Such failure can result in the ejection of particles of hot quartz arc tube that can ignite combustible materials below. Indeed, it is known that several serious fires have been caused in this way.


The Electricity at Work Regulations 1989 set out the particular legal requirements relating to the use and maintenance of fixed, portable and transportable electrical equipment and systems. They apply to all workplaces and are designed to prevent danger or the risk of injury.

The Institution of Electrical Engineers (IEE) Wiring Regulations for Electrical Installations, 17th Edition, are non-statutory regulations which form a code of practice that is widely recognised and accepted in the UK. Compliance with them is likely to achieve compliance with the Electricity at Work Regulations 1989. These Regulations are now incorporated in BS7671: 2008 Requirements for Electrical Installations.

Some Local Authority and Fire Authority licences also contain requirements and guidance on electrical matters.

Electrical Hazards

Regardless of size of premises or location, the electrical hazards can be grouped under the headings of Electric Shock/ Burns and Electrical Fires. It must be remembered that electricity can kill.

Electric shock or burns have a number of basic causes:

  • Physical contact with faulty electrical equipment or appliances due to lack of maintenance
  • Physical contact with damaged or exposed conductors
  • Poor condition of the general electrical installation
  • Lack of earthing conductors or earth leakage protective devices (RCDs)
  • Wrongly connected conductors making exposed metalwork live
  • Use of portable electrical equipment in wet areas

Electric shock has a variety of effects on the human body. Mild shocks cause an unpleasant tingling sensation; more severe ones cause muscle contractions, interfere with breathing and can upset the heartbeat; and severe shocks can cause extensive burns and are usually fatal.
Voltages in excess of 50 volts alternating current should be regarded as dangerous even in cool, dry conditions.

Electrical fires are caused by a number of hazards:

  • Overloading of conductors leading to overheating
  • Ignition of combustible materials or fabrics in contact with electrical equipment or unprotected light bulbs
  • Breakdown of insulation leading to current leakage causing sparks

Specific Precautions for HID's

  • Lamps should be used in accordance with the operating and installation instructions supplied by the manufacturer
  • Do not use any lamp that has been damaged or scratched. Physical damage may cause the lamp to fail unexpectedly.
  • Lamps must be kept well away from combustible elements of construction and from combustible materials
  • Where possible arrange stock so that lamps are within aisles to minimise the risk of hot particles falling onto combustible items in the event of an uncontained failure
  • Replacement of bulbs and other work should only be undertaken by properly qualified electricians and only when the lamps are cold and the power locked off
  • The lamp type and rating should be appropriate for the fitting and meet manufacturer's specifications
  • Do not modify existing fittings or retrofit non-approved containment barriers without manufacturers input and approval. Lamp rupture can be caused by incorrect heat dissipation.
  • For new installations the use of light fittings with integral containment barriers (i.e. borosilicate glass) fitted with the appropriate lamp type is preferred
  • Where containment barriers are not possible, a shroud is needed to protect the arc tube
  • As failure rate increases with age it is recommended that lamps should be changed at 70% of their rated life
  • Where lamps are operated continuously, they should be switched off for at least 15 minutes per week. Any defective lamps liable to fail should be picked up by this control procedure.
  • Bulbs that continually switch off then on again need to be replaced immediately as this indicates problems with the ballast or overheating

Key Action Steps

  • Ensure that the electrical installation as a whole complies with the 17th Edition IEE Wiring Regulations
  • Ensure that only competent persons carry out installation, maintenance, repairs and testing (e.g. NICEIC registered)
  • Make appropriate use of residual current devices (RCDs) to protect from electric shock
  • Undertake simple visual checks to ensure the electrical wiring and connections are in good condition
  • Ensure periodic electrical inspections and tests are carried out on the general electrical installation, the fire alarm and emergency lighting installation, and all portable electrical equipment
  • Ensure that the maintenance regimes take into account the specific precautions required for HID's
  • Keep a record of all test results


Memorandum of Guidance on the Electricity at Work Regulations 1989 HS (R) 25 HSE Books ISBN 0 11 883963 2.

IEE code of practice for in-service inspection and testing of electrical equipment.
ISBN 0 85296 844 2.

BS7671: 2008 Requirements for Electrical Installations (IEE Wiring Regulations)

The Management of Health and Safety at Work Regulations 1999 and Approved Code of Practice. L21 HSE Books ISBN 0 7176 2488 9.

IEE Guidance Note 3 Inspection and Testing

RISC Authority RC 37 Recommendations for the control of fire hazards arising from electrical lighting in commercial and industrial premises.

Next Steps:

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Please Note
This document contains general information and guidance and is not and should not be relied on as specific advice. The document may not cover every risk, exposure or hazard that may arise and Aviva recommend that you obtain specific advice relevant to the circumstances. AVIVA accepts no responsibility or liability towards any person who may rely upon this document.

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