Frequently Asked Questions

Here’s a few of the most frequently asked questions fielded by our engineers:

“My building has stood for 100 years, and has never been hit. So there's no chance of it being struck now!”

The probability of a strike and whether protection should be fitted will be shown by carrying out a risk assessment. York Minster was around 600 years old when it was ‘eventually’ struck by lightning in 1984, causing extensive irreplaceable damage. Remember a direct strike to the structure is not even necessary for lightning to cause damage through fire, electric shock or electronic systems failure.

“I have an air finial on the tallest part of the building and a down conductor, so that should be adequate?”

This is unlikely to give adequate protection in accordance with BS EN 62305 which calls for a full Faraday Cage, comprising a number of conductors on and around the building.

“How do I know if my building needs lightning protection and, if so, what level of lightning protection system (LPS) is required?”

There’s no intuitive way of doing this – you need to carry out a risk assessment in accordance with BS EN 62305:2006 Part 2.

The risk assessment in BS EN 62305-2 is much more detailed and has many more parameters than the assessment contained in BS 6651.Furse has developed a bespoke risk assessment software package to simplify and speed the process, called StrikeRisk. For a a free trial click here.

“I have looked at the number of parameters required to carry out a risk assessment, but cannot find all the information. What should I do?”

The risk assessment carries default values, which can be used where accurate information is not available. However, these values are conservative, so you should try and obtain as much accurate information as possible.

“Can I get a site survey to plan a surge protection system?”

Yes. Furse can do site surveys for surge protection – they are free on mainland UK.

Unfortunately we can’t check an existing structural lightning protection system or do a survey for one. You would need to call a specialist lightning protection installer.

“I have a lightning conductor system on my building - will this protect my electronics within the building?”

No, this will protect the structure itself but not the electronics within it. You therefore need specialist surge protection to prevent equipment damage from Lightning Electromagnetic Impulses (LEMP).

BS EN 62305 focuses on coordinated SPDs (Surge Protection Devices), where the locations and LEMP handling attributes of a series of SPDs are coordinated to nullify the conducted LEMP effects - thereby protecting equipment within their environment.

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