Skip image and navigation and go to main content

Omega Red The UK Market Leader in Electrical Earthing and Lightning Protection

BS EN 62305 Questions and Answers

Why was BS6651 withdrawn?

To take account of developments in Lightning Protection, the IEC has developed a new international governing standard. This standard was adopted by CENELEC, the European standards body and published as an EN standard in early 2006.

All member states of the European Union are required under the rules of CENELEC to withdraw their own National Standards and introduce the new European normalised document. The British Standards Institute published the standard BS EN 62305 in September 2006.

On what date did BS EN 62305 become applicable?

BS EN 62305 became applicable to all new projects commissioned since 1st September 2008.

What are the main differences between BS6651 and BS EN 62305?

There are many differences between the two standards but the three main ones are:-

A complex risk assessment must be carried out in all cases to determine what level of lightning protection (of which there are now four) is required to bring the risks inside defined tolerable levels.

There are now different types of risk to be assessed, namely R1 – Risk of Loss of Human Life, R2 – Risk of Loss of Service to the Public, R3 – Risk of Loss of Cultural Heritage and R4 – Risk of Loss of Economic Value.

Surge Protection now forms a normative part of the standard and, as a minimum, service entry surge protection devices are required in all cases where a structural lightning protection system is fitted.

What is the new risk assessment all about?

The risk assessment is a complex statistical tool which enables the lightning protection specialist to determine a level of risk relative to the specific parameters of the structure to be protected. The calculated risk is compared to tolerable levels of risk identified within BS EN 62305, resulting in appropriate protection measures designed to reduce the assessed risk to within those tolerable levels.

Is BS EN 62305 in use anywhere else in the world?

The 62305 standard is in use in many areas of the world but in different forms. In other parts of the world it may be in the IEC form, whilst in Europe it will be in the EN form. Each member state of the European Union has the right under CENELEC rules to add to the EN version of the standard in order to take account of their own nationally derived social values or perception of risk. The BS version amplifies certain areas of the EN standard by having UK derived annexes "NB", "NC", "NH" and "NK".

It is most important to use these UK derived annexes when applying the standard in the UK. The use of any other EN annexes would derive risk assessment outcomes that are not compliant with BS EN 62305.

Will my preferred Lightning Protection Contractor be able to provide systems to BS EN 62305?

That will depend upon the levels of training the contractor's personnel have received. ATLAS, the industry association, has accredited the competence of members' personnel to understand and apply the requirements of BS EN 62305.

To be sure that your contractor is competent and able to provide a service which ensures your potential liabilities are covered, check that their personnel have third party accreditation certificates issued by ATLAS.

Does it cost more to install systems to BS EN 62305?

That depends upon outcome of the risk assessment which takes account of the location, nature, usage and occupancy of the structure to be protected. BS EN 62305 offers enhanced engineering to that of BS6651 by considering the protection of human life and protection against transient over-voltages that damage electrical and electronic systems. In essence, you are not comparing like with like when looking at the two standards, so a direct price comparison cannot really be made.

How can I get more information on BS EN 62305?

Simply send your request to or call 0115 877 4444 and we will get one of our accredited lightning protection specialists to contact you.

What are the different risks that can be assessed and how are they determined?

There are four risks that may need to be assessed under the new standard. "Risk of Loss of Human Life" is an obvious risk that is likely to need to be determined in most if not all cases. "Risk of Loss of Service to the Public" is a loss that may be considered if a loss of service would be unacceptable to the public or indeed where such loss may expose a client to unacceptable financial losses or liabilities. "Risk of Loss of Cultural Heritage" is a loss that may be considered if the loss of a structure or its contents may be deemed unacceptable and "Loss of Economic Value" is almost academic as it has no tolerable level and merely produces coefficient values to input into a further calculation that determines theoretical cost or saving by the installation or otherwise of a lightning protection system.

Why do I need surge protection?

Under BS EN 62305, surge protection is a fundamental part of a lightning protection system. The purpose of lightning current surge protection is to protect against dangerous sparking to minimise the risk of loss of life and damage to the structure. Dangerous sparking can result in fire and electric shock hazards as it presents a risk of flashover, where the voltage present exceeds the withstand rating of the cable insulation or equipment subjected to this over-voltage.

Additional co-ordinated surge protection may be required to protect sensitive electrical and electronic equipment within the building or structure. The purpose of co-ordinated transient over-voltage surge protection is to protect electrical and electronic systems and equipment from the secondary effects of indirect lightning and switching transients, generated downstream of the lightning current surge protection.


Lightning Inspection, Test & Maintenance

Comprehensive, nationwide service.

more about lightning inspection, test and maintenance and complying with the law
Membership and Accreditation Logos

Terms and conditions of website use | Website purchasing terms | Privacy notice | Cookies.

A member of South Staffordshire Plc   A member of SSI Services