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MAINE EMERGENCY MANAGEMENT AGENCY
Lightning Awareness Week: Indoor Safety
June 23, 2011
The National Weather Service has declared the week of June 19th through 25th, Lightning Safety Awareness Week. This safety information is courtesy of the National Weather Service, Gray, Maine.
Safe Shelters and Indoor Safety
A house or other substantial building offers the best protection from lightning. In assessing the safety provided by a particular structure, it is more important to consider what happens if the structure gets struck by lightning, rather than whether the structure will be hit by lightning.
For a shelter to provide protection from lightning, it must contain a mechanism for conducting the electrical current from the point of contact to the ground. These mechanisms may be on the outside of the structure, may be contained within the walls of the structure, or may be a combination of the two.
On the outside, lightning can travel along the outer shell of the building or may follow metal gutters and down spouts to the ground. Inside a structure, lightning can follow conductors such as the electrical wiring, plumbing, and telephone lines to the ground.
Unless specifically designed to be lightning safe, small structures do not protect occupants from lightning. Many small open shelters on athletic fields, golf courses, parks, roadside picnic areas, schoolyards and elsewhere are designed to protect people from rain and sun, but not lightning. A shelter that does not contain plumbing or wiring throughout, or some other mechanism for grounding from the roof to ground is not safe. Small wooden, vinyl, or metal sheds offer no protection from lightning and should be avoided during thunderstorms.
There are three main ways lightning enters homes and buildings:
Regardless of the method of entrance, once in a structure, the lightning can travel through the electrical, phone, plumbing, and radio/television reception systems. Lightning can also travel through any metal wires or bars in concrete walls or flooring.
In the past, the use of corded phones was the leading cause of indoor lightning injuries in the United States. However, with more and more cordless and cell phones in use, the number of phone injuries has been diminishing. At the same time, the number of children injured while playing video games that are plugged into a wall or television has been increasing.
Lightning can travel long distances in both phone and electrical wires, particularly in rural areas. Stay away from windows and doors as these can provide the path for a direct strike to enter a home. Do not lie on the concrete floor of a garage as it likely contains a wire mesh.
In general, basements are a safe place to go during thunderstorms. However, there are some things to keep in mind. Avoid contact with concrete walls which may contain metal reinforcing bars. Avoid washers and dryers since they not only have contacts with the plumbing and electrical systems, but also contain an electrical path to the outside through the dryer vent.
Protect Your Property:
Lightning also causes significant damage to personal property each year. In addition to direct strikes, lightning generates electrical surges that can damage electronic equipment some distance from the actual strike.
To the extent possible, unplug sensitive electronic equipment from all conductors well before a thunderstorm threatens. For your safety, do not unplug equipment from the wall when a thunderstorm is nearby. And, don't forget to disconnect televisions or radios from outdoor antennas! If you plan to be away from your home when thunderstorms are possible, be sure to unplug unneeded equipment before you leave.
Summary of Lightning Safety Tips for Inside the Home
Lightning Fact for the Day: The average flash of lightning contains enough electricity to light a 100 watt light bulb for more than 3 months.
Lightning Question of the Day:
Is it safe to talk on a cell or cordless phone during a thunderstorm.
Compared to talking on a corded phone, the cordless phone is much less of a hazard. However, there is a momentary risk of being struck by lightning when the phone is being removed from the cradle. Once out of the cradle, it is safe to use a cordless phone during a thunderstorm, provided, of course, that you are in a safe place.
To learn more about lightning safety, visit the National Weather Service Lightning Safety page.
Last update: 07/20/10
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