Flammability of combustible materials in reduced oxygen environment

摘要

Flammability of combustible materials in reduced oxygen environment is studied using theoretical analysis and laboratory-scale experiments. The experimental results show that the limiting oxygen concentration (LOC) at extinction and re-ignition can be measured using a variable oxygen concentration technique with uncertainties of ±0.5% (vol.). The imposed external radiant heat flux only affects the LOC measurements for the fuels tested in this work when the flux is less than 30 kW/m~2. Comparison of measured LOCs in parallel panel and horizontal geometries suggests that the latter appear to be more conservative given the same total incident heat flux to the fuel surface. A validation parallel panel test for fire propagation using PMMA at 15% (vol.) oxygen concentration confirmed fire propagation when the ambient oxygen concentration is higher than, but approaching the measured LOC. LOC calculations using critical flame temperature and Spalding's B-number theory provide qualitative agreement with the experimental data. However, quantitative comparison of calculations and measurements shows that the calculated LOCs are sensitive to the selection of flame temperature. Furthermore, calculations also show that LOCs do not change significantly if the ambient temperature varies no more than 40 K. Based on the experimental results, most of the combustible materials studied in this work such as polyethylene, oak and corrugated paper board will not be adequately protected if the ambient oxygen is maintained at 15% (vol.) or higher.