Kerala - Thiruvananthapuram   

Understanding lightning to minimise the risk

File Photo

Play of light: A flash of lightning. —

THIRUVANANTHAPURAM: The North-East monsoon brings not only copious rainfall but also thunder and lightning. This is the time of the year when the southern districts of Kerala become vulnerable to lightning strikes, causing damage to life and property.

During the thunderstorm over the city on Thursday, lightning bolts struck several areas, destroying coconut trees and causing destruction of electrical equipment in houses.

To alert the public to the hazards of lightning and educate them on the precautions to be taken, the Centre for Earth Science Studies (CESS) has published a brochure titled ‘Lightning: Phenomenon and Precautions.’ The brochure is available on the web site of centre at cessind.org.

According to the literature, an understanding of the science of lightning can go a long way in reducing the risks associated with it. Lightning produces an electric potential of 100 million volts, heating up the air to a temperature of 30,000 degrees centigrade in a few tens of milliseconds. Shock waves produced in the process are propagated as thunder claps.

One of the most important things to be remembered is that a thunder cloud or lightning will be active in an area only for about one hour. So, observing a few precautions for an hour may save one from a serious injury. Locations surrounded partially or fully by unbroken metallic surfaces or nets do not allow lightning to penetrate to the interior and hence a person is safe inside. Examples are buildings of concrete with steel reinforcement (RCC). However, it is advisable to stay away from doors and windows and avoid water.

The brochure advises against using telephones and head sets during a thunderstorm. Turn off, unplug, and stay away from appliances, computers, power tools and TV sets. Unplugging power cord and antenna should be done preferably in the forenoon of a possible day of lightning occurrence.

Lightning may strike exterior electric, TV cable and phone lines, carrying energy to inside equipment. Keep away from all loose wires and wall sockets of power and telephone. If possible, keep away from large metallic objects such as stoves and ranges, bath tubs, furnaces, water and gas pipes, and also from electric lines especially at points where these enter the house from outside. Cordless or cell phones can be used cautiously inside a RCC roof building.

Steel-framed buildings and houses with sheet metal coverings on roofs and walls, with the joints connected electrically to ensure a complete conductive surface are considered safe. So also are automobiles with coherent metal bodies. Lightning prefers to strike the tallest of all objects in the location of strike. The greatest danger is under trees, especially just under low branches extending far sideways. All kinds of trees are dangerous, the taller the more vulnerable.

After hitting a tree, lightning energy enters the house through the ground. The lightning rod does not prevent this.

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