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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />Pressure Waves) <br />From simple dazzling to being struck dead by lightning, with a range of effects <br />Physiological <br />in between: Nervous shocks, various forms of blindness, deafness, blacking <br />out, and momentary or prolonged comas. <br />A common misconception of people being killed from lightning is because they were struck. Most lightning <br />injuries and deaths are causes by mechanisms other than direct lightning strikes. Only 3-5% of lightning <br />strike victims take a direct strike. 3-5% of lightning victims are contact injuries where the person is <br />touching or holding an object to which lightning attaches, such as indoor wired telephones or plumbing <br />that transmits current to the person. 30-35% of injuries are caused by a side flash, also called splash. Side <br />flashes occur when lightning hits an object such as tree or building and travels partly down that object <br />before a portion jump to a nearby victim. Most injury (50-55%) come from ground current. Ground <br />current arises because the earth is not a perfect conductor. Ground current effects are more likely to be <br />temporary, slight, and less likely to produce fatalities. However multiple victims and injuries are more <br />frequent from ground current. Another 10-15% of injury occur from upward leaders. Upward leaders are <br />upward discharges of lightning, which almost always occur from towers, tall buildings, or mountain tops. <br />A direct consequence to the body is an intense shock can severe impair most of the body's vital functions. <br />Cardiac arrest is common. Commonly when there is a strike that affects the heart directly, there is a <br />massive shutdown. With every beat the heart depolarizes and changes its electrical signal. In addition, <br />people can develop problems days, weeks, or months after being struck or being close to a lightning strike. <br />4.3.5.4. Potential for Cascading Effects <br />Lightning strikes that hit the ground, called cloud to ground strikes, can have a vast array of consequences. <br />One of the most common cascading events is when a lightning strike causes a fire to start, which can then <br />spread to homes, or produce wildland fire. Another consequence would be if lightning strikes a <br />transformer and people are without power for days, those people could be at risk for heat illnesses if hot <br />and humid conditions persist. <br />When lightning strikes a building, transients are generated on adjacent power, data, telephone and/or RF <br />lines. As these transients pass through electronic equipment on their way to earth, they can cause both <br />immediate damage and longer -term component degradation. However, the problem goes far beyond a <br />direct strike. Today our electronic systems are intrinsically connected to the outside world, not only by <br />mains power cables, but also through data and telephone lines, RF feeders, etc. Transient over voltages <br />from lightning activity up to 1 km away can destroy equipment inside a building, even when the building <br />itself has not been struck. As transients can be induced onto any conductive cable -overhead or <br />underground, the power, data, telephone, or RF lines leaving a building to join the main network or even <br />running between buildings can provide a way in for transients looking for a path to earth. Lightning simply <br />striking the ground, or even cloud -to -cloud lightning, induces a transient overvoltage on those cables, <br />allowing access directly into the electronic heart of that theoretically protected building. The following is <br />a list of possible secondary consequences following a lightning event. <br />• Downtime and disruption <br />• Hardware damage <br />111 <br />