Recently I was made aware of a report from Florida about lightning striking a metal septic tank, which caused it to explode. This event is probably pretty rare but nonetheless it can happen. This also got me thinking about how often we, as service providers, are working outside when thunderstorms approach and this is a matter of personal safety. Lightning strikes can be deadly if you are unlucky or unaware of your surroundings during storms.

According to the National Weather Service there are five ways a person can be struck by lightning. Any of these have the potential to be fatal and survival depends on the amount of charge and the ability to receive immediate medical attention. The five ways are direct strike, side flash, ground current, conduction and streamers.

• Direct strikes are when a person becomes part of the main lightning discharge path. They are not as common as other ways to be struck by lightning, but probably the most deadly. They usually occur when the person is out in the open.
• A side flash occurs when lightning strikes a taller object a foot or two from the person. This is what happens when standing under or next to a tree to avoid rain or hail.
• Ground current is when lightning strikes an object and travels outward in and along the ground. It can travel through garage floors as well. Anyone near the strike is subject to this current, it is the type that causes the most injuries and death. It also is responsible for the death of farm animals in the field.
• Conduction is where the current is transmitted through metal, which is a good conductor. This  in combination with the ground current is probably what happened with the metal septic tank.
• Streamers happen when lightning doesn’t make it to the ground but discharges causing fracturing charges to spread out in different directions. If you happen to be in contact with a streamer, you can be injured or killed even though the direct connection is not made.

LIGHTNING RODS

The speculation about lightning striking the septic tank centered on whether or not the tank was properly grounded. A metal tank would be a good conductor between the lightning and the earth. It is important for 

structures to be grounded or they can conduct current through the floor. This is accomplished with a lightning rod.

A lightning rod (or lightning protector) is a metal strip or rod connected to earth through conductors and a grounding system, providing a preferred pathway to ground if lightning terminates on a structure. The class of these products is often called a finial or air terminal. A lightning rod or Franklin rod — named for its famous inventor, Benjamin Franklin — is simply a metal rod, and without being connected to the lightning protection system, as was sometimes the case in the past, will provide no added protection to a structure.

The U.S. National Lightning Safety Institute advises anyone working outside to have a plan for their safety when a thunderstorm occurs and to commence it as soon as the first lightning is seen or thunder is heard. This is important, as lightning can strike without rain falling. If thunder can be heard at all, the risk of lightning exists.

One way to gauge distance to a lightning strike is to use the F-B (flash to boom) method. The flash of a lightning strike and resulting thunder occur at roughly the same time. But light travels 300,000 km/sec, almost a million times the speed of sound. Sound travels at the slower speed of about 340 m/sec (depending on the temperature), so the flash of lightning is seen before thunder is heard.

A method to determine the distance between lightning strike and viewer involves counting the seconds between the lightning flash and thunder. Then, dividing by three to determine the distance in kilometers, or by five for miles. Immediate precautions against lightning should be taken if the F-B time is 25 seconds or less, that is, if the lightning is closer than 8 km or 5 miles.

LIGHTNING TIPS

The report from the Lightning Safety Institute suggested it doesn’t matter whether a person was standing up, squatting or lying down when outside during a thunderstorm because lightning can travel along the ground. The report suggested being inside a solid structure or vehicle was safest.

Following is a list of Lightning Safety Institute safety measures to be followed to protect yourself and other workers.

• Do not move next to a high object such as a tree or near metal objects like poles and fences.
• Do not take shelter in car ports, open garages, covered patios, picnic shelters, beach pavilions, tents, sheds, greenhouses, golf shelters and baseball dugouts.
• Do take shelter in a building or a vehicle. It was reported that “the steel frame of a hard-topped vehicle can protect you from lightning” ... and “avoid using electronic equipment inside the car and avoid touching anything metal.”
• If inside a building, avoid electrical equipment and plumbing; do not take a shower.
• Risk remains for up to 30 minutes after the last observed lightning or thunder.
• It has been reported that “if you are on water, get to the shore and off wide, open beaches as quickly as possible as water will transmit strikes from further away. Studies have shown that proximity to water is a common factor in lightning strikes.”
• It has been reported that “if you do not have anywhere to go, then you should make for the lowest possible ground like a valley or ravine.”
• Do not huddle up “...with other people in a group — spread out from your friends as much as you can.”

As we approach spring and the presence of thunderstorms, keep yourself and the ones around you safe.