That concentration of a combustible material in air below which ignition will not occur. Note: Lower flammable limit is also known as the lower explosive limit (LEL). NFPA 329, 2005 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}