thousand volts per linear foot. This phenomenon (also responsible for reports of mass reindeer deaths due to lightning storms) leads to more injuries and deaths than the above three combined. EMPs – the discharge process produces an electromagnetic pulse (EMP), which may damage an artificial pacemaker, or otherwise affect normal biological processes. Hallucinations may be induced in people located within 200 m (650 ft) of a severe lightning storm. Secondary or resultant Explosions Fires Accidents Warning signs of an impending strike nearby can include a crackling sound, sensations of static electricity in the hair or skin, the pungent smell of ozone, or the appearance of a blue haze around persons or objects (St. Elmo's fire). People caught in such extreme situations – without having been able to flee to a safer, fully enclosed space – are advised to assume the "lightning position", which involves "sitting or crouching with knees and feet close together to create only one point of contact with the ground" (with the feet off the ground if sitting; if a standing position is needed, the feet must be touching). Injuries Lightning strikes can produce severe injuries, and are lethal in between 10 and 30% of cases, with up to 80% of survivors sustaining long-term injuries. These severe injuries are not usually caused by thermal burns, since the current is too brief to greatly heat up tissues; instead, nerves and muscles may be directly damaged by the high voltage producing holes in their cell membranes, a process called electroporation. In a direct strike, the electrical currents in the flash channel pass directly through the victim. The relatively high voltage drop around poorer electrical conductors (such as a human being), causes the surrounding air to ionize and break down, and the external flashover diverts most of the main discharge current so that it passes "around" the body, reducing injury. Metallic objects in contact with the skin may "concentrate" the lightning's energy, given it is a better natural conductor and the preferred pathway, resulting in more serious injuries, such as burns from molten or evaporating metal. At least two cases have been reported where a strike victim wearing an iPod suffered more serious injuries as a result. During a flash, though, the current flowing through the channel and around the body can generate large electromagnetic fields and EMPs, which may induce electrical transients (surges) within the nervous system or pacemaker