Fire Safety Science Digital Archive

In a fire, normally non-hazardous thermoplastic materials can produce lethal concentrations of toxic effluents in the smoke. The toxic product yields of the asphyxiants carbon monoxide (CO) and hydrogen cyanide (HCN) from developed fires are typically 10 times greater than those generated in small-scale laboratory fire test apparatuses. Since most fire deaths, and most fire injuries, result from inhalation of toxic effluents, accurate replication is important for both fire hazard assessment and forensic fire investigation. The stoichiometric equivalence ratio allows the ventilation condition of flaming fires to be compared across different scales. The yields of CO and HCN from five laboratory-scale methods have been compared to large-scale data under the range of flaming fire conditions. Toxic product yield data from the smoke density chamber (SDC) (ISO 5659-2), the controlled atmosphere cone calorimeter (CACC) (based on ISO 5660), the fire propagation apparatus (FPA) (ASTM E 2058), the French railway test (NFX) (NF X 70- 100), and the steady state tube furnace (SSTF) (ISO/DIS 19700) are compared to published large-scale enclosure fire data (from a standard ISO 9705 room) for two polymers, polypropylene (PP) and polyamide 6.6 (PA 6.6). The results from the SSTF and FPA show the best agreement with those from the full and ⅓ scale ISO room for both materials under a range of fire conditions. The CACC and SDC show reasonable agreement for well-ventilated burning, but fail to replicate the more hazardous under-ventilated fire conditions. The NFX generates data intermediate between the well-ventilated and under-ventilated fire conditions.