The Multi-Fuel WAPI (Water Pasteurization Indicator) is an excellent tool for effective water pasteurization, especially with a Sun Oven. The Multi-Fuel WAPI can be used when heating by campfire, Sun Oven, charcoal, propane, or any other type of fuel, and can be reused hundreds of times. This simple-to-use thermometer indicates when your water or milk has reached its pasteurization temperature (65 C/149 F) and is safe to drink. Pasteurization is a process that destroys virtually all disease-causing microorganisms from drinking water or contaminated water and milk. Pasteurizing potentially contaminated fluids prior to drinking is an absolute necessity, especially during a disaster or emergency. In use, the transparent tube is removed from the case and snapped into the hole provided in the bottom, with the wax end up. The case is placed in a pot, pan, or jar that is filled with water. When the wax has dropped to the bottom of the tube, the water is safe to drink. Since water pasteurizes at temperatures well below its boiling point, the Multi-Fuel WAPI saves time when solar pasteurizing, and saves fuel when using traditional heating methods. Made in the U.S.A!