Combustion and Flame 151 (2007) 551–559 www.elsevier.com/locate/combustflame Criteria for piloted ignition of combustible solids Richard E. Lyon a,∗ , James G. Quintiere b a Fire Safety Branch, Federal Aviation Administration, William J. Hughes Technical Center, Atlantic City International Airport, NJ 08405, USA b Department of Fire Protection Engineering, University of Maryland, College Park, MD 20742, USA Received 16 March 2006; received in revised form 10 June 2007; accepted 29 July 2007 Available online 10 October 2007 Abstract The onset of piloted ignition (flash point) of combustible polymers is predicted by a gas phase combustion energy density of 1.9 MJ/m 3 that describes the lower flammability limit of fuel vapor–air mixtures. The mass flux (1 g/m 2 s) and (virtual) heat release rate (24 kW/m 2 ) of the solid at incipient ignition derived from this observation are in general agreement with experimental data for piloted ignition of plastics. Sustained ignition marks the transition from lower-limit to stoichiometric burning and the critical heat release rate increases proportionally to 66 kW/m 2 . A critical heat release rate, unique among ignition criteria, is independent of material composition because of the implicit coupling between the gas and condensed phase processes. Published by Elsevier Inc. on behalf of The Combustion Institute. Keywords: Ignition; Plastic; Polymer; Ignition temperature; Heat release rate; Heat flux Nomenclature Symbols are defined as they are introduced in the text. Polymers are natural or unfilled materi- als obtained from suppliers or original manufac- turers: polyurethane rubber (PUR), polycaprolactam (PA6), polybutylene terephthalate (PBT), polycarbon- ate (PC), polyphenylene sulfide (PPS), polyphosph- azene rubber (PPZ), polyethylene naphthalate (PEN), polyetherether ketone (PEEK), polyphenylsulfone (PPSU), epoxy (EP), the cyanate ester of bisphenol- A (CE), polybenzimidazole (PBI), polyimide (PI), polyether imide (PEI), and polyamide imide (PAI), polyoxymethylene (POM), polymethyl methacrylate (PMMA), polyethylene (PE), polypropylene (PP), polystyrene (PS), polystyrene containing bromine- * Corresponding author. Fax: +1 (609) 485 6909. E-mail address: richard.e.lyon@faa.gov (R.E. Lyon). containing flame retardants (PS FR), unsaturated polyester thermosetting resin (UPT), acrylonitrile– butadiene–styrene polymer (ABS), chlorinated poly- vinyl chloride (CPVC), polyethylene–tetrafluoroeth- ylene (ETFE), fluorinated ethylene–propylene (FEP), polyhexamethylene–adipic acid (PA66), polytetrafluo- roethylene (PTFE), polyvinylidene fluoride (PVDF), and polyethylene terephthalate (PET). 1. Introduction Piloted ignition of solids and liquids occurs when a discrete source of energy such as a flame, spark, electrical arc, or glowing wire initiates combustion of the gases and vapors liberated by the condensed phase. Condensed phases will continue to burn if the energy input is sufficient to generate volatile, com- bustible fuel at a rate that will sustain flaming com- 0010-2180/$ – see front matter Published by Elsevier Inc. on behalf of The Combustion Institute. doi:10.1016/j.combustflame.2007.07.020