The key facts you need to know about arc flashes

By far one of the most underestimated dangers of working with electrical equipment, arc flashes are magnitudes more powerful than an average electric shock. In an instant, they can cause massive physical damage to inanimate objects and systems, as well as devastating and irreparable damage to the human body. And while they’re thankfully not hugely common, they’re also not as rare as many people think. Here at Rubber Box, electrical safety is a big focus of ours – it’s a key element in the design of our power distros – so we thought it was a subject worth revisiting both for professionals and amateurs alike.

What is an arc flash?

You may be familiar with the basics of an ‘arc’ already – essentially it’s a luminous bridge that’s formed in a gap between two electrodes. What’s happening is that electrical currents are ionising gases in the air. It’s a process that’s imbued with a serious amount of power – lightning strikes are one large-scale example in the natural world. and arcs are intentionally utilised for processes like welding and plasma cutting.

When it’s an unexpected, uncontrolled reaction though, it can have catastrophic consequences. It’s often the result of some kind of fault or short circuit condition, and can have a number of underlying causes, ranging from equipment that’s underrated for the short circuit current in question, or even the contamination, deterioration and corrosion of the equipment itself.

To the uninitiated, an arc flash might not sound all that worrying. The word ‘flash’ implies something silent and scary, but ultimately harmless. That’s not the case with an arc flash. They expel massive amounts of deadly energy, and can reach temperatures as high as 20,000 degrees. That’s hotter than the surface of the sun!

The dangers of an arc flash

We really can’t overstate how dangerous it is. Amongst other things, an arc flash is capable of:

• Setting clothing alight and burning skin enough to cause permanent scarring (and all from quite some distance)
• Igniting any combustible materials within the vicinity, such as wood or paper
• Liquefying or vaporising metal components, tools and equipment, potentially spraying molten metal across the immediate area
• Cause explosive pressure and sound waves loud enough to rupture eardrums, resulting in temporary or permanent hearing loss
• Creating pressure waves powerful enough to knock anyone nearby from precarious positions (such as from ladders), or even throwing them across the room
• Producing a bright enough flash that can cause temporary or permanent blindness

What kind of damage can an arc flash cause?

You don’t have to look far to find real-world examples of how damaging an arc flash can be. As recently as 2022, the operators of the Boulby mine in Yorkshire were fined £3.6 million following two serious arc flash incidents in 2016 and 2019, both of which resulted in severe burns to electricians. The first incident involved an electrician who suffered severe burns after inserting a vacuum cleaner nozzle into a live 11,000-volt chamber, while the second occurred when another contractor made contact with a live conductor during testing, leading to a hospitalisation.

During the following investigation, Health and Safety Executive (HSE) found significant deficiencies in Cleveland Potash’s risk assessment and safety procedures, noting that both incidents were easily preventable. The company ultimately admitted to health and safety breaches and was also ordered to cover £185,000 in court costs.

And before that, in 2020, the operators of the Sellafield nuclear site were prosecuted after a worker sustained burns from an arc flash while working on high-voltage electrical equipment at their site near Seascale on 24 April. The Office for Nuclear Regulation (ONR) accused the company of allegedly breaching the Health and Safety at Work Act. The company ended up paying £320,000, as well as £12,000 in costs.

How can you protect yourself and your staff from arc flashes?

The UK guidance on arc flashes remains frustratingly vague, and there is no specific legislation that deals with them. The HSG47 comes the closest, dealing with the risks posed by cable strikes, but the measures as they relate to arc flashes are still open to a lot of interpretation.

PPE is still one of the most reliable ways to safeguard human health and safety – Those working in utilities, the industrial electrical or petrochemical sectors are most at risk, so it’s worth having specialist PPE on hand if at all possible. Specialist garments are manufactured from inherent fibres that can protect against the very worst effects. They won’t guard employees against completely, but in a pinch they can make the difference between life and death.

Even with specialist PPE, there’s no one surefire way to protect yourself or your employees from the risks of an arc flash. Instead, the best way to mitigate them is to do everything you can to prevent one.

Stay informed, stay safe

You can start with making sure that everyone potentially at risk is fully informed of the possible dangers. After all, it’s no good having specialist PPE if people aren’t taking the hazards seriously enough to wear it! It’s also just as important to keep all equipment in good condition, and conduct regular risk assessments to ensure that everything meets the bare minimum safety standards. With electrical faults and being one of the chief underlying causes of arc flashes, using equipment in poor repair is a risk you can’t afford to take.

Be thorough on any inspections

Regular maintenance and inspection are essential to prevent arc flash incidents. Power distribution boxes (for example) will need to be inspected frequently for signs of wear, corrosion, or contamination that could compromise their safety. Your maintenance routine will also need to include checking for loose connections, ensuring that insulation is intact, and verifying that all protective devices are functioning correctly. It’s also important to clean equipment regularly to remove dust and debris that could cause electrical faults.

In addition to routine checks, performing thermal imaging can help identify hotspots and potential failure points before they lead to an arc flash. This proactive approach can help to give you plenty of time for repairs or replacements of faulty components, effectively reducing the risk of serious incidents. And of course, don’t forget to keep detailed records of maintenance activities and inspections, as these can help to reliably track the condition of equipment and ensures that safety standards are consistently met.

And one final thing – if you’re looking for new electrical distribution equipment, you’re in exactly the right place. Each of our power distros has been designed chiefly with safety in mind, and each has been issued with its own Certificate of Conformity. As well as our range of standard rubber boxes, we also offer the option for bespoke power distros – so if you can think of it, we can build it! Give us a call on 01282 677 910, and we’ll be happy to see how we can help!