Presentation Transcript

1. Lightning Safety 101 “If you can see it, flee it” “If you can here it, clear it”
2. Presented By:
3. What you will learn General Lightning information How lightning occurs Physics of lightning What is thunder? Types of lightning Lightning myths Odds of being struck Lightning casualties Lightning’s range Physical effects of lightning Vehicles and lightning safety How to protect yourself Flash to Bang Method First aid treatment Lightning plan
4. Lightning is a serious and life-threatening weather phenomenon, responsible for multiple deaths, injuries and massive property destruction throughout the United States. Unfortunately, lightning is alsothe most under-recognized weather hazard, often commanding little attention from the public and the media. There are some ten cloud-to-cloud lightning's for each cloud-to-ground lightning flash. Globally, some 2000 on-going thunderstorms generate about 50-100 lightning strikes to earth per second.
5. The phenomenology of lightning flashes to earth, as presently understood, follows an approximate behavior: The downward Leader (gas plasma channel) from a thundercloud pulses toward earth. Ground-based air terminators such as fences, trees, blades of grass, corners of buildings, people, lightning rods, power poles etc., etc. emit varying degrees of induced electric activity. They may respond at breakdown voltage by forming upward Streamers. In this intensified local field some Leader(s) likely will connect with some Streamer(s). Then, the "switch" is closed and the current flows. Lightning flashes to ground are the result. A series of return strokes follow.
6. Lightning is a giant spark of electricity in the atmosphere or between the atmosphere and the ground. In the initial stages of development, air acts as an insulator between the positive and negative charges in the cloud and between the cloud and the ground; however, when the differences in charges becomes too great, this insulating capacity of the air breaks down and there is a rapid discharge of electricity that we know as lightning. Lightning can occur between opposite charges within the thunderstorm cloud (Intra Cloud Lightning) or between opposite charges in the cloud and on the ground (Cloud-To-Ground Lightning). Cloud-to-ground lightning is divided two different types of flashes depending on the charge in the cloud where the lightning originates.
7. Thunder is the sound caused by a nearby flash of lightning and can be heard for a distance of only about 10 miles from the lightning strike. The sound of thunder should serve as a warning to anyone outside that they are within striking distance of the storm and need to get to a safe place immediately! Thunder is created when lightning passes through the air. The lightning discharge heats the air rapidly and causes it to expand. The temperature of the air in the lightning channel may reach as high as 50,000 degrees Fahrenheit, 5 times hotter than the surface of the sun. Immediately after the flash, the air cools and contracts quickly. This rapid expansion and contraction creates the sound wave that we hear as thunder.
8. Intra-cloud lightning is an electrical discharge between oppositely charged areas within the thunderstorm cloud. Cloud-to-ground lightning is a discharge between opposite charges in the cloud and on the ground. Cloud-to-ground lightning can either occur between negative charges in the cloud and positive charges on the ground (a negative flash) or between positive charges in the cloud and negative charges on the ground (a positive flash).
9. Lightning never strikes the same place twice. (Lightning often strikes the same place repeatedly, especially if it’s a tall, pointy, isolated object. The Empire State Building is hit nearly 100 times a year.) Rubber tires on a car protect you from lightning by insulating you from the ground. (Most cars are safe from lightning, but it is the metal roof and metal sides that protect you, NOT the rubber tires. Remember, convertibles, motorcycles, bicycles, open-shelled outdoor recreational vehicles and cars with fiberglass shells offer no protection from lightning. When lightning strikes a vehicle, it goes through the metal frame into the ground. Don't lean on doors during a thunderstorm.) If outside in a thunderstorm, you should seek shelter under a tree to stay dry.(Being underneath a tree is the second leading cause of lightning casualties. Better to get wet than fried!) If trapped outside and lightning is about to strike, I should lie flat on the ground.(Lying flat increases your chance of being affected by potentially deadly ground current. If you are caught outside in a thunderstorm, you keep moving toward a safe shelter.)
10. General Lightning Facts: (From NOAA, unless otherwise noted) Number of thunderstorms occurring at any given moment - 2000 Number of lightning strikes every second - 100 Number of lightning strikes per day - 8 Million Number of thunderstorms in the USA per year - 20 Million Number of VOLTS in a lightning flash - 30 million Number of AMPS in a lightning flash - between 10,000 and 200,000 The average lightning flash would light a 100 watt light bulb for 3 months. Lightning has been documentedto strike over 25 miles away from the actual thunderstorm.
11. The top ten states in number of lightning casualties (deaths and injuries combined). Florida leads the list, with twice as many casualties as any other state. Other states represented are Georgia, Tennessee, North Carolina, New York, Pennsylvania, Ohio, Michigan, Colorado and Texas.
12. When you hear thunder, you are already within the range where the next ground flash may occur. The National Lightning Safety Institute and Central Lightning Protection, Inc. of Japan determined the average intervals between lightning strikes in order to estimate how much time someone has to seek shelter. Their news is far from encouraging. "It is concluded that there exists no safe time interval during which a human is free from direct strikes," they wrote. Important new information about lightning may affect sensitive facilities. First, the average distance between successive cloud-to-ground flashes is greater than previously thought. The old recommended safe distance from the previous flash was 1-3 miles. New information suggests that a safe distance should be 6-8 miles.
13. Most doctors are more familiar with electrical shocks, such as those received by industrial workers when they have an accidental run-in with high-voltage equipment. But lightning injuries are not the same as electrical shocks. For one thing, the contact voltage of a typical industrial electrical shock is 20 to 63 kilovolts, while a lightning strike delivers about 300 kilovolts.
14. Industrial shocks rarely last longer than half a second (500 milliseconds) because a circuit breaker opens or the person is thrown far from the live conductor. Lightning strikes have an even shorter duration, only lasting up to a few milliseconds. Most of the current from a lightning strike passes over the surface of the body in a process called "external flashover.“ Both industrial shocks and lightning strikes result in deep burns at point of contact - for industry the points of contact are usually on the upper limbs, hands and wrists, while for lightning they are mostly on the head, neck and shoulders. Industrial shock victims sometimes exhibit deep tissue destruction along the entire current path, while lightning victims’ burns seem to center at the entry and exit points. Both industrial shock and lightning victims may be injured from falling down or being thrown, and the leading cause of immediate death for both is cardiac or cardiopulmonary arrest.
15. If you survive a shock, you still have to deal with the consequences of the electrical burns. Industrial shock burns can lead to kidney failure, infection, muscle and tissue damage, or amputation. Lightning burns are exceptionally life threatening.
16. Reported incidents and related injuries make it clear that a person inside a fully enclosed metal vehicle must not be touching metallic objects referenced to the outside of the car. Door and window handles, radio dials, CB microphones, gearshifts, steering wheels and other inside-to-outside metal objects should be left alone during close-in lightning events. We suggest pulling off to the side of the road in a safe manner, turning on the emergency blinkers, turning off the engine, putting one's hands in one's lap, and waiting out the storm. Damage. Reported damage to vehicles includes pitting, arcing, burning on both exterior and interior places. See the below photographs, courtesy of Mr. Brown, of his Jeep Cherokee which was struck by lightning. Cases have been reported of total destruction of vehicle wiring, and associated electrical and electronic systems. Cases from police departments report bad burns to the hands and mouth where officers were using radio microphones when their vehicles were struck. Cases describe total blow-out of all four tires in passenger cars. A video in our NLSI library shows a station wagon being struck by lightning in a heavy rain storm, with no damage whatsoever occurring.
17. So how to achieve lightning safety? It is a personal decision. Your decision. At the first sign of lightning or thunder, seek shelter. Good shelters are substantial buildings or fully enclosed metal vehicles. We suggest you remain in shelter for 30 minutes after the last observed thunder or lightning. "If you can hear it, clear it. If you can see it, flee it."
18. There are 2 things to remember about lightning safety. First, how close should you let the lightning get to you before implementing your lightning safety plan of action, and second; how much time should elapse before resuming outdoor activities. To estimate the distance between you and a lightning flash, use the "Flash to Bang" method: If you observe lightning, count the number of seconds until you hear thunder. Divide the number of seconds by five (5) to get the distance (in miles) the lightning is away from you. Flash to Bang Method
19. If you are caught in the open and lightning is nearby, the safest position to be in is crouched down on the balls of your feet. Do not allow your hands (or other body parts) to touch the ground, and keep your feet as close to one another as possible. Why is it important to crouch down on the balls of your feet. The reason why is that when lightning strikes an object, the electricity of the lightning discharge does not necessarily go straight down into the ground. Quite often the electricity will travel along the surface of the ground for quite a large distance. This is know as a "side flash". Many people who are "struck" by lightning are not hit directly by the main lightning channel, but are affected by the side flash as it travels along the surface of the ground (this can be is especially true if the ground is wet). By keeping the surface area of your body relative to the ground to a minimum (that is, keep your feet together and do not allow any other part of your body to contact the ground [see picture below]), you can reduce the threat of the electricity traveling across the ground from affecting you.
20. Immediate symptoms of Lightning Injury: Most victims experience only some of the symptoms below. Short-term memory Problems coding new information and accessing old information Problems Multitasking Slower reaction time Distractibility Irritability Personality change Inattentive Forgetfulness Intense headaches Ringing in the ears Dizziness Nausea and vomiting and other post-concussion types of symptoms Difficulty sleeping, sometimes sleeping excessively at first and then only two or three hours at a time
21. Most people struck by lightning are not struck directly, but are affected by the current running through the ground (also known as a "side flash"). People who are adversely affected by a lightning flash, either directly or indirectly, need prompt medical attention: Call 911. Provide directions and information about the likely number of lightning strike victims; The first tenet of emergency care is "make no more casualties". Any rescuer must be aware of the continuation of danger that a lightning storm poses to the rescuers as well as to the victim(s). If the area is a high risk area (under a tree, mountain top, open field, etc.), it may be better that the rescuers who are in a relatively safer area wait until the danger has passed before exposing themselves.
22. It is relatively unusual for victims who survive a lightning strike to have major fractures that would cause paralysis or major bleeding complications unless they have suffered a fall or been thrown a distance. As a result, in an active lightning storm, if the rescuers choose to expose themselves to the lightning threat, it may be better to move the victim away from the area of risk (such as under a tree, etc.) rather than to give medical attention at the spot of the initial flash. Rescuers are reminded to stay as low as possible and provide as little area to the ground surface as possible. If the victim is not breathing, provide mouth to mouth resuscitation . If the victim has no pulse, (check for the pulse at the carotid [neck] or femoral [knee] artery for 20 -30 seconds). then start CPR. If the area is cold and wet, putting a dry article of clothing between the victim and the ground may decrease the threat of hypothermia that the victim suffers which can complicate the resuscitation.
23. The lightning safety plan of action must be known by all employees onsite. Plan Ahead! Make sure someone in the group gets a good weather forecast before starting work. Designate one of the members of the group to monitor NOAA weather radio (which can be purchased at most electronics stores, such as Radio Shack) or a portable radio. This way you will always be able to get the latest forecast. Once arriving on-site, know how far away safety is in case lightning threatens. Remember to account for the time it will take for all employeesto get to asafe location. If thunderclouds do begin to develop, make sure a designated personcontinuously monitors the sky for lightning.
24. Example: You are a safety coordinator at your facility. You are aware of a lightning storm which is 15 miles to your west, and it is moving east at 30 mph (or 1/2 a mile per minute) towards your location. You know it will take approximately 10 minutes to get people into a safe location. How close should you let the storm get to your location before issuing the "lightning alarm"? First, you know that people should already be in safe shelter when lightning is within 6 miles of the event site. As safety coordinator, what you need to know then is: How long will it take for the storm to get within 6 miles of the events location. If the storm is moving east (towards you) at 30 mph, then it is moving at the rate of 1/2 a mile per minute. In the 10 minutes it takes to seek safe shelter, the storm will move 5 miles  [ 1/2 (mile/min) x 10 (minutes)  = 5 miles ]. Based on this storm motion and the time it takes people to get into shelter, the warning should be issued when the storm is 11 miles (6 miles from event + 5 miles storm will travel in 10 minutes = 11 miles) away from the event site. In the example above, if you issued the lightning alarm when the storm was 5 miles from the events location, it would be too late to get everybody in a safe location. This is because it takes time (in this case, 10 minutes) to get everybody to a safe shelter.