When lightning strikes

WITH reference to the lightning incident earlier this month in Setia Alam, Shah Alam, that killed one person and seriously injured several others (“One killed in lightning strike”, Nation, The Star; online at bit.ly/star_lightning):

Those affected were in the middle of a football field surrounded by tall trees and buildings, some with lightning rods on them.

The man who died was reportedly using a cell phone when he was struck by lightning, and his clothes were set on fire as a result of the strike.

This scenario raised several questions that need to be answered so the public can understand how lightning work.

Why did the lightning bolt strike the victims instead of the tall trees and buildings around the field?Observations by scientists have revealed that lightning has an average “striking distance” of about 50m, ie, it will strike anything within this range.

Hence, if the trees and buildings are beyond this range as the lightning descends to the ground, it will strike the surface of the field immediately below it or anything on the field, such as people, animals, goal posts, flag poles, tents, etc.

Why did the lightning bolt not strike the lightning rods on top of a nearby building?Lightning is not attracted to any object, metal or non-metal. A lightning rod, whether conventional or non-conventional, does not attract lightning. It will only intercept a bolt if it comes within the bolt’s striking distance.

Did the use of a cell phone lead to the victim being struck by a lightning bolt?Definitely not. Neither the metal components of the cell phone nor its emitted radiation can attract a lightning bolt.

How did the lightning bolt strike several victims at the same time?A single lightning bolt can have more than a dozen separate lightning strokes in quick succession. High-speed photographic studies have shown that most of these strokes will strike at a single object but some strokes may reach nearby objects.

Victims of lightning strikes can suffer fatal or near fatal injuries such as brain injuries, heart stoppage and skin burns. Victims further away can suffer temporary paralysis in the legs as current flows between them as a result of each leg standing on different voltage levels.

The following lightning safety rules have been posted in the past as a guide to prevent people from being struck by lightning.

1. Stop all outdoor activities and seek shelter as soon as you see dark thunder clouds gather on the horizon or over the hill. Lightning can strike up to 15km away from the thunderclouds, and even before the rain starts.

2. Run for shelter if you can hear thunder or see a lightning bolt. You are already in danger of being struck by lightning.

3. Do not wait for the rain to fall before you act. Sometimes, lightning occurs before the rain starts to fall. Never use an umbrella in a lightning storm.

4. Do not take shelter under a tree or in a tent, a small shed, a rotunda or a roadside food stall. If you take refuge in a small shelter, ensure that it has a proper lightning protection system before you enter it.

5. Do take shelter inside a sturdy or large building (eg, a shop or a house), inside a metal roofed vehicle or under a large structure (eg, a bridge). Do not loiter outside a large building to avoid being struck by debris from lightning damage.

6. If there is no proper shelter nearby, get down from elevated positions (eg, mound, hilltop or platform). Get into any depression in the ground or into a dry drain.

7. Get into a lightning defensive position, ie, squat down with your feet together and cover your ears with your hands. Do not lie down. do not touch anyone or any metal object (eg fence, gate, etc) near you.

8. If it rains, get your clothes wet because wet clothing helps to reduce serious injuries on a lightning-struck person. Let the current flow over you instead of inside you.

9. Inside your shelter, do not touch any metallic object, electric equipment or cable. Do not use a land-line telephone unless it is really urgent. Use a mobile phone instead (if available). Keep away from the balcony, verandah, doorway, window, wall or pillars.

10. Stay inside your shelter for 30 minutes after the last sound of thunder is heard. Lightning can strike up to 15km away from thunderclouds, even after the rain has stopped.

Z.A. Hartono

Lightning protection

researcher and consultant