A boiler is a closed vessel in which water or other fluid is heated under pressure. The fluid is then circulated out of the boiler for use in various processes or heating applications. Construction of boilers is mainly limited to copper, steel, stainless steel, and cast iron. The source of heat for a boiler is combustion of any of several fuels, such as wood, coal, oil, or natural gas. Electric boilers use resistance or immersion type heating elements. Nuclear fission is also used as a heat source for generating steam. Heat recovery steam generators use the heat rejected from other processes such as gas turbines.
Boiling Point Meters are used to indicate accurate local barometric pressure and the boiling point of water. These readings are useful in making syrup and added value maple products, such as cream, sugar.