Hydrogen cyanide in fire tests

Abstract

The gas composition of fire smoke depends on the material being burned. Plastics containing nitrogen, e. g. polyurethane, which are used in modern household furnishings release hydrogen cyanide (HCN) under the influence of heat. In order to evaluate the impact of HCN on the ability of victims to react and escape possibilities as well as on the cause of death, the concentration of HCN and other gaseous components of smoke were determined by burning materials containing polyurethane. Bench scale fire tests (smouldering fires) were performed using model sofa samples containing polyurethane. The concentrations of HCN, carbon monoxide (CO) and carbon dioxide (CO2) were measured using Fourier transformation infrared (FTIR) spectroscopy. Additionally, the oxygen (O2) consumption, transmission and optical smoke density were determined. The gaseous concentrations in smoke determined in the bench scale fire tests were compared with the results of an enclosed room fire test (developing fire to full fire). The average maximum concentrations measured were 42 ppm for HCN and 1100 ppm for CO. The measured values can be classified as toxic to humans but are not in the fatal range. In relation to the dominant CO concentration during smouldering fires, the HCN content in fire smoke can only be considered as having a low-grade influence on human poisoning; however, if material containing polyurethane is burned in a full fire the HCN concentration must be considered as at least a contributing factor to the death of fire victims.