British Thermal Unit (BTU) 14 : The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit at atmospheric pressure
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}