Safe Shelters and Indoor Safety

I'm meteorologist John Jensenisus with the National Weather Service. I'm here to tell you what is and what is a not a lightning safe shelter. Also, I'll let you know what you should and shouldn't do while inside. A house or other substantial building offers the best protection from lightning. To determine the safety provided by a structure, it's more important to consider what happens if the structure gets hit by lightning rather than whether the structure will be hit by lightning. For shelters to provide protection from lightning, it must contain a mechanism to conduct the electrical current from the point of contact to the ground. These mechanisms may be on the outside of the structure, 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 and may follow metal gutters or downspouts to the ground. Inside a structure, lightning can follow conductors such as electrical wiring, plumbing and telephone lines to the ground. Unless it's specifically designed to be lightning safe, small structures do little, if anything, to protect occupants from lightning. Many small open shelters on athletic fields, golf courses, roadside picnic areas, school yards and elsewhere are designed to protect people from rain and sun, but not lightning. Shelters that do not contain plumbing or wiring throughout or some other mechanism for grounding from the roof to the ground are not safe. Small, wooden, vinyl or metal sheds provide no protection from lighting and should be avoided during thunderstorms.

There are three main ways lightning enters homes and buildings: direct strike; through wires or pipes that extend outside the structure or through the ground. Regardless of the method of entry, once inside, lightning can travel through electrical and phone lines, plumbing, and radio and TV reception systems. Lighting can also travel through any metal wires or bars in concrete walls or flooring.

Phone use is the leading cause of indoor lighting injuries in the U.S. 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 a path for a direct strike to enter a home. Do not lie on the concrete floor of a garage as it likely to contain a wire mesh. In general, a basement is a safe place to go during a thunderstorm. However there are a few things to keep in mind. Avoid contact with concrete walls as they 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 through the outside through the dryer vent. Lightning also causes significant damage to personal property each year. In addition to direct strike, lightning generates electrical surges that can damage electronic equipment some distance from the electrical strike. To the extent possible, unplug any appliances or electrical equipment from all conductors well before the thunderstorm threatens. Don't forget to disconnect televisions and 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.

Here's a summary of lightning safety tips for inside the home: Stay off porches. Stay away from windows and doors. Avoid contact with corded phones and with electrical equipment or cords. If you plan to unplug any electrical equipment, do so well before the storm arrives. Avoid contact with plumbing. This includes washing your hands, taking a shower or bath, washing dishes or doing laundry. If you want more information about lightning safety, go to www.lightningsafety.noaa.gov