Weather Safety - Kifissiameteo.gr

WEATHER LESSONS - Storm, Lightning Safety

Whole-Home protection systems

Founding father and inventor Ben Franklin can be credited for the beginnings of modern Lightning Protection Systems. Franklin observed that lightning tends to strike elevated objects, and that a network of conductors and grounding electrodes can carry lightning currents safely away from structures and into the earth to dissipate. Over 200 years later, such systems still do the job, and are all the more vital since contemporary structures contain far more conductive material than those built in Ben's day.

The three main Lightning Protection Systems components are air terminals, conductors, and ground electrodes. Air terminals, also known as lightning rods, are placed at intervals on a home's roof and any high points projecting from it, and are designed so that lightning strikes them instead of the building. Conductors are the cables that run from among the air terminals to the ground electrodes, where lightning's charge is sent safely into the earth.

For thorough lightning protection, you'll also need a complete network of connections which could include vent fans, gutters, water pipes, home electrical systems, phone lines and other vital connections. Between this and the tricky rooftop Lightning Protection Systems installation requirements, it's best to get the help of an experienced installer to set up your system.

Pros are also needed to install surge arrestors, which protect your wiring and electrical equipment should a lightning-induced power surge travel down a power line toward your home. Surge arrestors are installed either outside where the electric service enters a building or at the inside service entrance, supplying a ground so that a power surge can't enter the structure.

Lightning can strike anywhere and do millions of money worth of damage. Lightning is to blame for more deaths and property loss than tornadoes, hurricanes, and floods combined. And although we cannot yet predict where lightning will strike, there are some factors that increase the risk of a lightning strike. If your home or business meets 5 or more of the following criteria, you are in a high risk group.

Has had previous lightning damage.
Is located in an isolated, open area.
Is located on a hill.
Located near a large body of water.
Is located in an area that has a high number of thunderstorms.
Has tall trees overhanging the roof.
Has metal, brick or stone chimney brick.
Has metal ridge vent.
Has aluminum siding.
Has no surge protection.

As homes and businesses use more sensitive electronic equipment, it might be a smart idea if every building has a lightning protection system. This would prevent millions of money spent in replacing or repairing damaged equipment.

Lightning Protection Systems - What they do and don't do

A lightning protection system's only purpose is to ensure safety to a building and its occupants if lightning happens to hit it directly, a task accomplished by providing a good, safe path to ground for the lightning to follow. Contrary to the myths, lightning protection systems:

   Don't attract lightning.
   Don't and cannot dissipate or prevent lightning by 'draining' a storm of its charge.
   Most don't offer surge protection for sensitive electronics.
   Do offer fire protection and structural damage protection by preventing a hot, explosive lightning channel from passing through building materials.

Lightning Protection Facts

   Rods and protection systems don't attract lightning, nor do they influence where lightning will strike.
   Rods or protection systems do not and cannot prevent lightning, nor can they 'discharge' thunderstorms.
   Lightning protection systems (including placement of rods, cables, and groundings) are custom-designed for individual structures and require complex engineering to function properly. They should only be installed by qualified contractors.
   Lightning protection systems do not always prevent damage to electronics or computers. You should still unplug such devices during thunderstorms to ensure sufficient protection.

How the Lighting Protection System works

PHASE: I

A lightning strike consists of opposite charges of electrical energy. A negative charge or build-up occurs in the bottom part of the cloud closest to earth and a positive charge of energy occurs directly underneath in the ground. Separating these two opposite charges is the non-conducting dry air belt separating cloud and earth. As the two opposite charges continue to build up and the dry air belt becomes moist, lightning starts dovn toward earth in 150 foot jagged steps or intervals. The positive ground charge is attracted upward, utilizing the lightning protection system on the building as an outlet.

PHASE: II

As the negative leader stroke from the cloud continues toward earth, the positive ground charge travels up through the Lightning Rod System and when the negative leader stroke is about 150 feet above the top of the protected building, the positive ground charge starts upward to meet and neutralize the downward leader stroke.

PHASE: III

In Figure 3, the two opposite charges are neutralized emptying the negative charges from the cloud and dissapating the ground charge. This all occurs in about one five thousands of a second.

PHASE: IV

In Figure 4, the discharge has been completed and the negative cloud charge and the positive ground charge becomes zero.

Note: If the residence had not been equipped with a lightning protection system, the positive ground charge would have accumulated under or within the house. The negative cloud charge would not have been neutralized 150 feet above the residence and would have entered the building, causing possible fire, destruction, side flashes within the building or even injury or death.

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Personal Lightning Safety

When storm approaches safety

If you are outside and you notice a storm brewing, do you know what to do? Here are a few safety tips:

Keep an eye on the sky, watch for well-defined darkening cumulus clouds, and listen for thunder.
If you see a flash in the sky, start counting "one one thousand, two one thousand, three one thousand", and so on until you hear thunder. Take that number and divide it by 5. This will let you know how many miles away the approaching storm is. For every five seconds the storm is 1 mile away.
If the storm approaches, seek shelter in a building (preferably with lightning protection) or car.
Once inside, turn off all appliances, stay off the phone, and avoid taking a shower or running the water. A lightning surge can enter the house through all of these.
If you are not able to get indoors, go to a low-lying open area away from trees, poles, and anything metal.
Assume the safety position. Make yourself a small target. Squat low to the ground, place your hands on your knees and put your head down low. Do not lie flat on the ground.
If you are trapped in the woods, take shelter under the shortest trees in the area.
If you are boating or swimming, get out of the water immediately and seek shelter.
If you are trapped in a boat, seek the lowest area away form anything metal, and assume the safety position.
If someone has been struck, administer first aid immediately and call for help. Do not be afraid to handle the person, they carry no electrical charge.

Indoor safety during a storm

Once you've got a lightning protection system in place, you may think you're safely indoors ahead of the storm. Well, you're not. Lightning can still impact home systems and your use of them, so the following precautions should be taken:

Shut down your air conditioner, as a lightning-induced power surge can overload and damage its compressor.
Avoid using the telephone (especially the corded variety) unless it's an emergency.
Avoid contact with electrical equipment or cords, and unplug any equipment possible before the thunderstorm arrives (if you're going to be away from home during thunderstorm weather, unplug all unnecessary equipment before you go).
Avoid any tasks that involve contact with pipes or running water, that means no use of sinks or showers, and no laundry chores.
Don't lie on concrete floors or lean against concrete walls.
Stay off of your porch or deck, and steer clear of windows and doors while you're inside the house.
Draw blinds and shades over windows so that if windblown objects hit and break them, shattering glass won't scatter into your home.
Remember that outdoor dog houses aren't usually lightning-safe shelters; bring all pets indoors to safety before a storm.

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General Lightning Safety Rules

1		-EN- Before a storm comes, take shelter in a sturdy building. -GR- Πριν καταφθάσει η καταιγίδα, βρείτε καταφύγιο μέσα σε ένα μεγάλο κτίριο.

2		-EN- Unplug appliances and do not use the telephone. -GR- Βγάλτε από την πρίζα όσες ηλεκτρικές συσκευές έχετε. Επίσης μην χρησιμοποιείτε τις τηλεφωνικές συσκευές κατά την διάρκεια της καταιγίδας.

3		-EN- Do not take a bath or shower. -GR- Φροντίστε να μην βρίσκεστε στο μπάνιο ή στο ντους, ο κεραυνός είναι πιθανόν να περάσει διαμέσου της υδραυλικής εγκατάστασης του κτιρίου.

4		-EN- Stay away from tall objects like trees, fences and power lines. -GR- Κρατηθήτε σε ασφαλή απόσταση από ψηλά σημεία όπως δένδρα, φράχτες και εναέρια καλώδια ρεύματος ή τηλεφώνου.

5		-EN- Avoid natural lightning rods like golf clubs, fishing rods, bicycles and camping equipment. -GR- Αποφύγετε να κρατάτε μεταλλικά αντικείμενα τα οποία είναι δυνατόν να τραβήξουν τον κεραυνό όπως καλάμια ψαρέματος, μπαστούνια του γκόλφ, ποδήλατα ή εξοπλισμό κατασκήνωσης γενικά.

6		-EN- If there is no shelter nearby, get into a car and roll up the windows. -GR- Αν δεν υπάρχει καταφύγιο κοντά σας μπείτε στο αυτοκίνητο σας και ανεβάστε τα τζάμια, αν το αυτοκίνητο σας δεν έχει μεταλλικό ουρανό δηλ. είναι "κάμπριο" τότε δυστυχώς δεν σας παρέχει καμμία προστασία...

7		-EN- When you feel the electrical charge (if your hair stands on end or your skin tingles) lightning may be about to strike you. Drop to the ground immediately. If you are in the woods, make yourself into a small ball. Put feet together. Place hands over ears to minimize hearing damage from thunder. -GR- Όταν νοιώθετε τα μαλλιά στο κεφάλι σας να ανορθώνονται και το δέρμα σας να ανατριχιάζει τότε έχει αρχίσει να σχηματίζεται το ηλεκτρικό πεδίο και σε λίγα δευτερόλεπτα ο κεραυνός πρόκειται να σας κτυπήσει. Αν βρισκόσαστε έξω και δεν υπάρχει καταφύγιο κοντά σας, καθήστε όπως στο σχήμα προσπαθώντας να μειώσετε τον όγκο του σώματος σας όσο το δυνατόν πιό πολύ ΧΩΡΙΣ ΝΑ ΑΚΟΥΜΠΑΤΕ ΤΑ ΧΕΡΙΑ ΣΑΣ ΣΤΟ ΕΔΑΦΟΣ, κλείστε με τα χέρια τα αυτιά σας ώστε να μην πάθουν βλάβη από τον ήχο του κεραυνού.

8		-EN- If boating, get out of the water immediately and go to shelter. -GR- Αν βρισκόσαστε μέσα σε βάρκα ή γενικά μικρό πλεούμενο, βγείτε γρήγορα στην ξηρά και αναζητήστε καταφύγιο.

9		-EN- Listen and watch for information on when it is safe to come out. -GR- Αναζητήστε πληροφορίες για το πότε είναι ασφαλές να βγήτε έξω. Και μήν ξεχνάτε το ασφαλέστερο είναι να βγήτε αφού έχει περάσει τουλάχιστον μισή ώρα από το τέλος της καταιγίδας, δέν είναι λίγα τα περιστατικά που κεραυνός έπληξε περιοχή τουλάχιστον 15 χμ από την περίμετρο της καταιγίδας.

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Top-10 Myths of Lightning Safety

1	MYTH: Lightning Never Strikes the Same Place Twice. TRUTH: Lightning often strikes the same place repeatedly, especially if it's a tall pointy isolated object. The Empire State Building used to be used as a lightning laboratory, since it is hit nearly 25 times a year. Places prone to lightning are places to avoid when thunderstorms are nearby!.

2	MYTH: If it's Not Raining, Or If Clouds Aren't Overhead, I'm Safe from Lightning. TRUTH: Lightning often strikes more than three miles from the thunderstorm, far outside the rain or even thunderstorm cloud. 'Bolts from the Blue', though infrequent, can strike 10-15 Miles from the thunderstorm. Anvil lightning can strike the ground over 50 Miles from the thunderstorm, under extreme conditions. Lightning in clouds has travelled over 100 miles from the thunderstorm.

3	MYTH: Rubber Tires Protect You from Lightning in a Car by Insulating You from the Ground. TRUTH: Lightning laughs at two inches of rubber! Most cars are reasonably safe from lightning. But it's the metal roof and metal sides that protect you, not the rubber tires. Thus convertibles, motorcycles, bicycles, open shelled outdoor recreational vehicles, and cars with plastic or fibreglass shells offer no lightning protection. Likewise, farm and construction vehicles with open cockpits offer no lightning protection. But closed cockpits with metal roof and sides are safer than going outside. And don't even ask about sneakers!

4	MYTH: A Lightning Victim Is Electrified. If You Touch Them, You'll be electrocuted. TRUTH: The human body doesn't store electricity. It is perfectly safe to touch a lightning victim to give them first aid. This is the most chilling of lightning myths. Imagine someone dying needlessly, for want of simple CPR or mouth-to-mouth resuscitation, when their chance of survival was 90%!

5	MYTH: If Outside in a Thunderstorm, Go Under a Tree to Stay Dry. TRUTH: Being underneath trees is the second leading activity for lightning casualties – enough said?!

6	MYTH: I'm In a House, I'm Safe from Lightning. TRUTH: While a house is a good place for lightning safety, just going inside isn't enough. You must avoid any conducting path leading outside, such as corded telephones, electrical appliances, wires, TV cables, plumbing (including plastic pipes with water in them), metal doors or window frames, etc. Don't stand near a window to watch the lightning. An inside room is generally best.

7	MYTH: When Playing Sports and Thunderstorms Threaten, It's Okay To Finish the Game before Seeking Shelter. TRUTH: Sports is the activity with the fastest rising rate of lightning casualties. No game is worth death or life-long severe injury. All people associated with sports should have a lightning safety plan and stick to it strictly. Seek proper shelter immediately when lightning threatens. Adults are responsible for the safety of children!

8	MYTH: Structures With Metal, Or Metal On The Body (Jewellery, Watches, Glasses, Backpacks, Etc.), Attract Lightning. TRUTH: Height, pointy shape, and isolation are the dominant factors controlling where a lightning bolt will strike. The presence of metal makes virtually no difference on where lightning strikes. Mountains are made of stone, but receive many strikes each year. When lightning threatens, take proper protective action immediately. Don't waste time shedding metal off your body, or seeking shelter under inadequate structures. But while metal doesn't attract lightning, touching or being near long metal objects (fences, railings, bleachers, vehicles, etc.) is still unsafe when thunderstorms are nearby. If lightning does happen to hit it, the metal can conduct the electricity a long distance (even over 100 yards) and still electrocute you.

9	MYTH: If Trapped Outside and Lightning Is About To Strike, Lie Flat On The Ground. TRUTH: This advice is decades out of date. Better advice is to use the 'Lightning Crouch': put your feet together, squat low, tuck your head, and cover your ears. Lightning induces electric currents along the top of the ground that can be deadly over 100 Feet away. While lying flat on the ground gets you as low as possible, which is good, it increases your chance of being hit by a ground current, which is bad. The best combination of being low and touching the ground as little as possible is the 'Lightning Crouch'. But the 'Lightning Crouch' should be used only as a last resort. Much better would be to plan outdoor activities around the weather to avoid thunderstorm exposure and to have proper shelter available.

10	MYTH: Go near a tall pointy isolated object when thunderstorms threaten, to be within the 45° "cone of protection". TRUTH: The "cone of protection" is a myth! While tall pointy isolated objects are statistically more likely to be struck by lightning, it's not nearly reliable enough to rely on for safety. Lightning can still strike you near the tall object. Besides, the lightning electricity will likely spread out along the surface of the ground and can still kill you over 100 Ft from the "protecting" object. Also, if you are close to or touching the tall object, you can be electrocuted via side flash or contact voltage. NO PLACE OUTSIDE IS SAFE NEAR A THUNDERSTORM! In lightning safety, a "myth" is not as good as a smile ☺. Distance and proper shelter is your best protection from lightning.

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