Indicates when Water has reached Pasteurization Temperatures; NOT A WATER PURIFIER Perfect for Camping, Hiking, Backpacking Essential for Emergencies Reusable Made in the USA Be prepared in an emergency! This water pasteurization indicator (WAPI) tells you when your water is safe to drink. Suspend the WAPI, wax end up, in a container of water and place in the SUNFLAIR solar oven. The wax inside melts at water pasteurization temperature (149 F). When the wax has melted down to the bottom of the tube, the water is safe to drink. Flip it over and reuse again and again. Ideal for campfires, stove tops, and other methods too!