Do you know that you could be in danger from lightning even inside your home?

 Photo by Leanne Lee

Lightning is the “visible discharge of static electricity within a cloud, between clouds or between the earth and a cloud,” as defined by Underwriters Laboratories. Lightning is unpredictable and a serious threat to buildings and their occupants virtually everywhere.

Facts about lightning:

  • Benjamin Franklin invented the first lightning rod in 1752 –- a kite outfitted with a metal key — while waiting impatiently for the completion of a church on top of which he would mount a lightning rod.

  • Lightning comes up from the earth –- as well as down from the cloud — from high vertical features such as chimneys and trees.

  • A typical lightning bolt carries 50,000 amps, tens of millions of volts, and can reach 50,000° F. “Superbolts” may be 100 times more powerful than typical bolts, and travel much farther, too; one such superbolt went from Waco to Dallas, Texas, after having traveled about 118 miles.

  • According to the National Weather Service, of the 34 people killed by lightning in the United States in 2009, all were outside when they were struck. Thus, homes provide a great deal of safety against lightning strikes. Interestingly, the same report indicates that 82% of lightning casualties were male.

  • Permanent injuries caused by lightning strikes are predominantly neurological and can include sleep disorders, attention deficits, numbness, dizziness, irritability, fatigue, depression, and an inability to sit for long periods of time.

  • Between 2002 and 2005, lightning caused an annual average of $213 million in property damage.

Types of dangers from lightning to houses and occupants:

  • damaged appliances from power surges;

  • electrocution risk for occupants;

  • fire risk to the building and occupants;

  • damage to the structure from water used to douse the fire by the fire department; and

  • damage to the structure and endangered health from mold colonies, if the building was not dried quickly following fire suppression.

Safety tips during thunderstorms:

  • Unplug sensitive appliances, such as computers and telephones, from electrical outlets and phone lines. Surge protectors are helpful, but they should not be relied upon during a storm.

  • Stay off corded phones, computers, and other electronic equipment that put you in direct contact with electricity. If you are unable to unplug them, turn them off. Lightning may strike nearby electric or phone lines and enter your home.

  • Unplug other appliances, such as air conditioners.

  • Stay away from windows.

  • Avoid washing your hands, bathing, doing laundry, and washing dishes — activities that put you in direct contact with running water.

Lightning Protection Systems

Lightning protection systems are devices intended to divert lightning into low-resistance paths to or from the earth and away from non-conducting parts of a structure. For specific inspection instructions regarding these systems, see the National Fire Protection Agency’s NFPA-780.

Lightning Rods

Metal rods are fastened to the building to intercept electric discharges that might otherwise strike a building component itself, such as a chimney or metal roof. Electrical discharges striking the air terminal are directed through metal conductors to a grounding system and thence into the earth.

Controversy has existed for centuries concerning whether lightning rods should have blunt or sharp tips. Recent studies have found that moderately blunt metal rods are better lightning-strike receptors than sharper rods or very blunt rods.

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