The effect of (NH4)2HPO4 and (NH4)2SO4 on the spontaneous ignition properties of Pinus halepensis pine needles

The spontaneous ignitability of Pinus halepensis pine needles was evaluated. Fire points and times taken for irradiated fuels to be ignited were correlated, at given heat intensity, to the airflow around the specimen and the sample size. The tests showed that increase of the airflow rate above 1.5 lmin 1 increased considerably the fire point values and ignition delay times. On the contrary, the sample size in the range investigated (0.2–1.0 g) showed a negligible effect on the ignition properties. The influence of fire chemical retardants (NH4)2HPO4 (DAP) and (NH4)2SO4 (AS) on the ignitability characteristics was studied under various concentration levels. The data in this study showed that the presence of DAP and AS increases the fire point, as well as the time required for ignition, and this effect is pronounced at high concentration levels. However, at lower temperatures, i.e. below 5001C, flaming combustion appears sensitive to the AS quantity applied, whereas at high temperatures (i.e. above 6001C) the DAP concentration had a major influence on its flammability behavior. In addition the time of combustion was slightly extended, therefore, the energy release rate was reduced in the presence of fire retardants, particularly of AS. The purpose of this study was to quantify the fire extinguishing capabilities of (NH4)2HPO4 and (NH4)2SO4, commonly used chemicals in forest fires, by comparing the ignition properties of samples, prior and after retardant loading. r 2002 Elsevier Science Ltd. All rights reserved.