Wednesday, May 19, 2010

Extreme Heat Survival

Summer is upon us, and with it comes fun in the sun and time spent playing at the beach, in the woods, or at your local sports field. But with the summertime sun comes the dangers of exposure to extreme heat.

Survival in extreme heat is a skill that everyone should have. It doesn’t take much for anyone from all walks of life to suddenly find themselves in a dire situation. You don’t need to be stranded in the desert or lost in a steamy jungle to be subject to the threat of high temperatures. Whether you find yourself stranded on a sun-baked highway or stuck in a heat wave, this guide will help you survive the extreme heat.

Extreme Heat Is Deadly
Heat waves have some of the highest mortality rates of all weather phenomenon. The CDC reports that between 1979 and 1999 there were 8,015 heat-related deaths in the United States alone. When severe weather strikes it often leaves thousands or even millions without the power to run an air conditioning or fans. In 1995 a heat wave killed approximately 600 people in Chicago in only 5 days. As recently as 2003 a heat wave in Europe killed more than 52,000 people. In the aftermath of Hurricane Katrina many people who survived the hurricane succumbed to the suffocating heat and humidity.

Image courtesy of Paulo Otávio, licensed under Creative Commons.

One of the leading causes of death in both the Chicago and European heat wave was poor air circulation and a lack of air conditioning. Some residents in Chicago decided not to open their windows at night for fear of crime. Other residents decided not to run fans or air conditioning due to the increased cost of power consumption. These decisions ultimately and unfortunately led to death in some cases.

There are three things you must consider when you need to survive in an extremely hot environment: water, shade, and activity level. Failure to take any one of these things into account can result in a dire situation very quickly.

Planning Activity Levels
Development of a buddy system is crucial to make sure that the elderly and infirm are taken care of in a heat wave. Buddy systems are also a good way to keep yourself safe. Often the victim of heat illness does not realize that they are succumbing to the heat because of the effect that heat has on the brain. With a buddy, you can keep an eye on them, and they on you, so that you have a second set of eyes watching for possible symptoms of heat stress. Prior to being in an extreme heat situation you should have a plan on what to do when faced with the problems that severe heat brings. Begin by taking an inventory of the tools, equipment, and materials that you have access to. Address the need for shade and water first, then focus on ways to establish an airflow or other cooling system. Include in your plan a schedule on when to engage in any physical activity at times when any heat will have a minimal impact.

Plan to have outdoor activity curtailed, and indoor activity limited to areas that can be kept cool. All activity you do raises your body temperature. The more vigorous the activity, the faster and higher your temperature goes and the more your body must work to keep you cool. If you must engage in outdoor activity in the heat, try to limit your work to the early morning hours when it is the coolest. While walking or working in the heat, breathe through your nose and keep conversation to a minimum to reduce moisture loss through respiration.

One of the best defenses to high heat is hydration. The human body requires water to function, and sweating in high heat depletes that water supply. In extreme heat, it is possible to lose as much of 2.5 liters of sweat per hour. All of that water and electrolytes must be replaced, so hydration is key. It is much more difficult for your body to stay cool if you are dehydrated. Hydration is not only necessary for sweat, but it also helps regulate body temperature by making it more difficult for the body to heat up rapidly. Heating up a liter of water just one degree requires almost 4000 BTUs (British Thermal Units). If your body is missing those 2.5 liters of water it is that much easier for the heat to raise your body temperature, and your body will need to sweat that much more to keep you cool.

Drink water whenever you are thirsty. Going without water in an attempt to conserve supplies may seem like a good idea, but because of water’s importance in maintaining body temperature you should always drink when thirsty to maintain hydration. If you find yourself running low on water, seek other sources, but under no circumstances should you ration water in an extremely hot environment. The risk of overheating increases exponentially as you become dehydrated. Hydration backpacks are a convenient way to carry around as much as 3 liters of water.

As important as proper hydration is the maintenance of a proper electrolyte balance. Hyponatremia is a condition that can lead to coma or death, and is caused by sodium levels in blood plasma that are too low. Symptoms can include nausea, vomiting, and headache, although most victims exhibit no symptoms whatsoever before dropping into a coma. Hyponatremia can occur through the loss of electrolytes through sweat, or through the over consumption of water (water intoxication). If you are sweating profusely and not replenishing the lost electrolytes, you can become affected by Hyponatremia. For this reason, when in an extremely hot environment, always remember to replenish electrolytes when you rehydrate. A teaspoon of salt per quart of water is all you need to maintain the right balance of sodium in your blood plasma. A healthy adult can process up to 15 liters of water per day. When hydrating, the important thing to remember is that liquids should be consumed over a period of time, not consumed all at once. To prevent Hyponatremia from excess water consumption, make sure that you consume no more than a half liter of water every 15 minutes.

Plan to have at least one gallon of water per person per day for drinking, but don’t neglect the cooling properties of water. Pools, cold showers or baths, or even lakes and streams are important resources to take advantage of in the heat.

Shade and Shelter
Shade or shelter is extremely important to protect you from radiant heat from the sun. Even if the air temperature isn’t that high, intense solar radiation can actually heat your body up to a much higher temperature. Because of this, shade is key to keeping cool. When considering the construction of a shelter in an emergency situation, try to keep your shelter elevated at least 12″ above the ground. The sun’s rays can heat up the ground as much as 30 degrees hotter than the ambient air temperature. Even resting in the shade on a stool or branch will keep you much cooler than sitting on the ground. If you must be exposed to direct sunlight, wear a light-colored, wide-brimmed hat or use a scarf and a loose fitting long-sleeved, light-colored shirt and pants. If the heat is still too much, try soaking your scarf or hat in water. The water will cool your skin and evaporate the same as sweat will. By keeping your skin temperature below 92 degrees you will minimize sweating and the moisture loss associated with it.

Air conditioning is the easiest way to stay cool in the heat, but if you do not have air conditioning, you will need to take other measures to stay cool. Consider going to public areas with air conditioning if they are available. During heat emergencies, most municipalities make public facilities such as libraries, community centers, or sporting arenas available for the public to use as a refuge from the heat.

Even if air conditioning is not available, it’s important to have air flow from fans or some other source. Air circulation is vital in helping the body to stay cool. When your body becomes over heated it opens up capillaries near the surface of the skin and sends a message to sweat glands, signaling them to release sweat. The sweat evaporates into the air, and the evaporative cooling effect then reduces the temperature of the skin as well as the blood in capillaries near the skin. That cooler blood is circulated throughout the body to maintain proper body temperature. Without air circulation however, the sweat is not able to evaporate as easily. Stagnant air makes evaporative cooling from sweat less efficient. While you do not want high wind, some airflow is necessary to maximize the cooling efficiency of sweat. A high wind in a hot environment acts as a convective oven, increasing the heating effect on you while at the same time increasing dehydration.

If you are indoors and have electricity but no air conditioning, keep windows closed in the morning and utilize fans for airflow. The radiant heat from the sun rapidly heats up the air outdoors, but the building’s insulation will keep it cooler than the outside air. As the day heats up, it will become necessary to open windows to move hot stagnant air out of the building and allow breezes to cool the indoors. By opening windows on the windward side of the structure as well as the leeward, you can create a cross flow of air through the building.

If you have the equipment, you can set up an evaporative cooling system. With electrical power, swamp coolers (also known as evaporative coolers) or fan-powered misting systems can be utilized to cool the air. These systems work best in low humidity environments where a fine mist is sprayed into an airstream. The tiny water droplets quickly evaporate into the air, causing a 15-20 degree drop in temperature. Swamp coolers are similar and use materials soaked in water over which air is blown. Again, the water in the material evaporates into the air, causing a 15-20 degree drop in air temperature from the evaporative cooling. Even without a powered fan, misting systems can still be incredibly effective at reducing the surrounding air temperature. These systems are available commercially, but they can also be easily constructed by a qualified individual from a fan and some plumbing parts. Always exercise caution when working around water and electricity.

Surviving Extreme Heat
A variety of tactics and techniques can be used to combat heat stress both in an urban and in a survival environment. If you have a plan for the situation you will find yourself at an enormous advantage and better able to beat the heat. By staying cool and hydrated in the shade and planning your activities around the hottest parts of the day you will be able to endure even the worst heat that mother nature can muster

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