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What is a Safe Shelter?
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 downspouts to the ground. Inside
a structure, lightning can follow conductors such as the
electrical wiring, plumbing, and telephone lines to the
ground.
Avoid Unsafe Shelters!
Unless 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, 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 little or no protection
from lightning and should be avoided during thunderstorms.
How Lightning Enters a House or Building
There are three main ways lightning enters homes and
buildings: (1) a direct strike, (2) through wires or pipes
that extend outside the structure, and (3) through the
ground. 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.
Stay Safe While Inside
Phone use is the leading cause of indoor lightning injuries
in the United States. 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.
Remember Your Pets
You may want to consider the safety of your family pets
during thunderstorms. Dog houses are not lightning-safe.
Dogs that are chained to trees or chained to wire runners
can easily fall victim to a lightning strike.
Protect Your Personal 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. Typical
surge protectors will NOT protect equipment from a lightning
strike. To the extent possible, unplug any appliances
or electronic equipment from all conductors well before
a thunderstorm threatens. This includes not only the electrical
system, but also the reception system. 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