Combustible Gas Indicator 4 : An instrument that samples air and indicates whether there are combustible vapors present and may also indicate the percentage of the lower explosive limit of the air-gas mixture
NFPA 329 Recommended Practice for Handling Releases of Flammable and Combustible Liquids and Gases, 2005 ed. https://www.nfpa.org/assets/files/AboutTheCodes/32 9/329-F2009-ROP.pdf, (Recmm Prac: Hndlg Releases of Flamm and Comb Liqd and Gas - Amer) {299 NFC}
Ingenieurbro Frank Markmann, Fire, Arson & Explosion Investigation in Germany and Europe, Fire Investigators Dictionary (The English definitions 1995 Edition of NFPA 921 Guide for Fire and Explosion Investigation), Wald, Germany (Revised 2008), http://www.fmfire.de/fidicteg.html, (FrInv - Brit) {94}
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}