five preconceived ideas about the precautions to take (or not)

At the end of August, two Italian cyclists, including the “king of panettone” Alberto Balocco, were struck down in the Alps while traveling with electrically assisted mountain bikes. The battery of the two machines may have increased the risk… but nothing is less certain.

New violent storms are expected over a large part of the country this week, and in particular this Tuesday in Bourgogne-Franche-Comté and Auvergne-Rhône-Alpes. This is an opportunity to take stock of what should (or not) be done to best protect yourself.

1. No, the tires do not protect against lightning

In the event of a storm, many think they are safe in the car thanks to the rubber tires which “insulate” them. This is wrong – in the car as well as on the bike.

In the car, it is the phenomenon of the “Faraday cage” which protects passengers and drivers, on two conditions: that the bodywork is metallic, and that the vehicle is closed.

To put it simply, when lightning strikes a closed conductive “container”, the electrical charge travels across the entire surface and is “balanced” there, without passing through the interior, before being evacuated through the ground. The power of a flash is such that the tires, which are also mounted on metal structures, do not insulate.

Still, to “benefit” from it, you must not be in contact with a metal part linked to the outside… nor be in a vehicle – including caravans – that is not metallic (fiberglass, plastic, etc.). And even less so in a convertible or… on a bicycle: the “Faraday cage” effect requires an enclosed cabin. And bikes, usually metal, can increase the risk, whether electric or not.

2. Yes, it’s best to unplug electrical appliances, but…

This is a frequent instruction: at home, electrical appliances must be unplugged in the event of a storm. This measure is mainly intended to protect them from a powerful overvoltage. Even if recent installations are more resistant to lightning, it can also cause a fire, or “indirectly” strike a person handling them: a flash can produce up to 40,000 amperes of electrical intensity.

If you unplug them, you must do so before the storm, especially not during it. And avoid letting the plug hang in the immediate vicinity of the socket.

For the same reason, it is strongly discouraged to telephone during a thunderstorm with a wired device. On the other hand, a mobile phone does not pose any particular problem… provided that it is not in charge!

3. No, you shouldn’t take shelter in a bathroom

Any indoor shelter is better than staying outside. But if you have the choice, some places are still to be avoided.

Lined with tiles and often far from the outside, does the bathroom seem like a good idea to you? Bad pick: the piping – metallic and therefore conductive – can be formidable. It is therefore better to take shelter in a “dry” room rather than in the kitchen or the bathroom.

It’s worse if you decide to take a bath or do the dishes: to the risk of the pipes is added that of the water, in direct contact with you.

Finally, it is advisable to close doors and windows tightly, more to avoid violent drafts and the dispersion or even breakage of objects than to avoid being struck by lightning – even if this risk cannot be totally excluded:

During a thunderstorm, air masses move rapidly and carry particles which ionise by friction against each other. They constitute a privileged channel for the lightning current

Lightning Protection Association

4. No, the danger does not come (only) from the trees

The storm sometimes occurs when you are outside – especially at work, the first “place” of thunderstorms, according to the Lightning Protection Association (APF). And sometimes without the possibility of returning to a closed shelter.

In any case, you must avoid taking shelter under a tree at all costs. But this instruction, among the best known, should not make us forget the essential: it is not the tree itself, which poses a problem, but its height, especially if it is isolated. And contrary to another received idea, oaks are not struck more often than other species. But they are often higher!

The higher and more isolated a potential “shelter” is, the more dangerous it will be. To choose, it is better to be in the heart of a dense forest of trees of the same height than under a fragile high artificial shelter, in the middle of nowhere.

Ideally, the APF advises to stay away from any high object likely to be struck by lightning. Recommended position: squatting on the ground, feet together, and especially not in a group: at least three meters between each person.

Finally, it is absolutely necessary to avoid running, because of the phenomenon of “step tension”, or to move “uncovered” under an umbrella, the metal tip of which constitutes a danger.

5. Yes, lightning can strike the same place twice (and it often does)

“Lightning never strikes twice in the same place”: who has never heard this phrase, suggesting that a past problem will not happen again? Regarding storms, it is false: witness, for example, the famous Empire State Building in New York, on which lightning strikes several dozen times a year.

And this is even the case, in general, of any isolated and high-rise place (bell tower, electric pole, large building, etc.).

Each year, in France, among the approximately 200 people struck by lightning, about 10% die, and 70% of survivors retain serious sequelae (serious cardiovascular and neurological disturbances, psychological trauma and shock, hearing and visual damage, etc.).

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