Pressure Cooking at High Altitudes Every high altitude cook should own a pressure cooker. Sea level is arbitrarily defined as zero. When you live at 5,000 feet above sea level, for example, the atmospheric pressure is 18% or 2.1 pounds less than at sea level. Every increase in elevation decreases it further. The pressure cooker has gained recognition for quick cooking, and vitamin -and-energy-saving features, but at high altitudes it provides the additional benefit of accomplishing the otherwise impossible. By enabling you to increase the pressure inside the cooker to nearer that of sea level, the pressure cooker raises the temperature at which water boils and makes food cook more quickly and thoroughly. Using the Pressure Cooker at High Altitudes At High Altitude (3500-6500 ft) cooks really have to plan ahead to do some of the same things the rest of us take fro granted. The reason foods have high altitude instructions is because the boiling point of water changes with altitude. As you go higher, the boiling temperature decreases. At sea level, the boiling point of water is 212° F (100° C). As a general rule, the boiling point temperature decreases by 1 degree F for every 540 feet of altitude (0.56° C for every 165 meters). On top of the14,000 foot Pike's Peak, for example, the boiling point of water is 187° F (86° C). Figuring Altitude in Pressure Cooking In order to cook at elevations above 2000 feet, the cooking times in a standard pressure cooker must be altered according to a very specific formula: For every 1000 ft above 2000 ft elevation, increase the cooking time by 5%. Using a little basic physics we know that water boils at 212°F at sea level, but as altitude increases the temperature at which water boils decreases at the rate of 1.9°F for each 1,000 feet because there is less atmospheric pressure on the surface of liquids. By adding 5PSI, water boils at about 16°F higher than it naturally would at that altitude; at 10PSI it boils at 28 °F higher, and at 15PSI, water boils 38°F higher. Therefore, by increasing the pressure, as in a pressure cooker, the temperature at which water boils is raised and the food is cooked more quickly. A standard pressure cooker operating at 15 PSI, rises the boiling point of water to 250°F (121°C) at sea level. At 240°F (which corresponds to only 10.5 PSI) the cooking times must be increased by 33% in comparison to the standard 15PSI. Boiling Point Of Water* Altitude in Feet Altitude in Meters Degrees F. Degrees C. 0 0 212.0 100.0 500 152 211.0 99.4 1000 305 210.0 98.9 2000 610 208.2 97.9 3000 914 206.2 96.8 4000 1219 204.4 95.8 5000 1524 202.6 94.8 6000 1829 200.7 93.7 7000 2134 198.7 92.6 8000 2438 196.9 91.6 10,000 3048 194.0 90.0 12,500 3810 189.8 87.7 14,000 4267 187.3 86.3 * = These temperatures will all vary according to whatever your current barometric pressure is. The ONLY way to find the exact boiling point is to take standard barometric pressure (29.92 millibars) and subtract the local barometric pressure (found on a barometer or in the local weather forecast). Multiply the resulting number by 1.8518. Add 212 to that and you will find the current boiling point of water wherever you happen to be at the time of testing (altitude does not matter). If you use this formula to find the boiling point, the result will only be correct for a short while because the barometric pressure is always changing. You'll need to get an updated local barometric pressure and refigure the formula. Additional Help You can often find more assistance from your local County Extension Agent, or Farm Advisors Office. These people have all kinds of handy booklets, leaflets and FAQ sheets to hand out for free or for a small charge. Check in your phone directory under State or County Government listings. Some offices will have a home economist available, or refer you to an expert for the help you need. Many state extension offices, state universities and junior colleges have their own websites where you can find info on food safety and high altitude cooking. Some offer extensive information online with many resources available to viewer. Another resource is your local high school, junior collage or university Home Economics department. You can often visit the teachers or call them for help.