Joule 13 : The preferred SI unit of heat, energy, or work; there are 4. 184 joules in a calorie, and 1055 joules in a British thermal unit (Btu). Note: A watt is a joule/ second. NFPA 921, 2004 ed
National Fire Protection Association, Illustrated Dictionary of Fire Service Terms, Jones & Bartlett Publishers, MA. USA 2006. https://books.google.com.kw/books?id=W0WIRa3Gl4QC& printsec=frontcover&source=gbs_ge_summary_r&cad=0# v=onepage&q&f=false, (Fr Srvc - Amer) {141}