Lightning: Safe Shelter and Indoor Safety
When Thunder Roars, Go Indoors -- but Where?
A house or other substantial building offers the best protection from lightning. In assessing the safety provided by a building, consider what happens if the structure gets struck by lightning, rather than whether the structure will be struck. In fact, on average, lightning causes about 4400 house fires and 1800 other structural fires each year, some of which are deadly. All totaled, lightning causes nearly $1 billion in damages each year.
For a shelter to provide protection from lightning, it must be able to conduct the electrical current from the point of contact to the ground. The mechanisms to do this may be on the outside of the structure, contained within the walls, 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, lightning can follow conductors such as the electrical wiring, plumbing, and telephone lines to the ground.
Most 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:
- A direct strike,
- Through wires or pipes that extend outside the structure, and
- Through the ground
Regardless of how it enters, 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.
Lightning safety inside the home
- Avoid contact with corded phones
- Avoid contact with electrical equipment or cords.
- Unplug electronic equipment, such as computers and video games, WELL BEFORE the storm arrives.
- Avoid contact with plumbing. Do not wash your hands, do not take a shower, do not wash dishes, and do not do laundry.
- Stay away from windows and doors, and stay off porches.
- Do not lie on concrete floors and do not lean against concrete walls.
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 plumbing and electrical systems, but also contain an electrical path to the outside through the dryer vent.
Avoiding lightning damage
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.
- 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.)
- Disconnect televisions or radios from outdoor antennas.
- Unplug unneeded equipment before you leave for any stretch of time during the warm weather when thunderstorms are likely.
For More Information
- National Weather Service, Gray, Maine: Lightning Safety
- NOAA: Lightning Safety Awareness
- Preparing Your Family for Emergencies