PubMed · 12645579
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Jana Howder. 2003. Clarification.. https://doi.org/10.1097/00152193-200303000-00003
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The minimum ignition energy of premixed gases has been calculated by using two theoretical expressions and compared with the experimental data. One expression considers the amount of energy that the minimal flame should have, and the other the heat loss from the surface of the minimal flamelet. The former is a cubic function of the quenching distance while the latter is a quadratic function of quenching distance. It has been found that the latter expression gives a better fit to the experimental data than the former, though the discrepancy is considerable even for the latter expression. The calculated widths of the fronts of the minimal flame for various fuels were about one-order of magnitude smaller than the corresponding experimentally determined quenching distances, although no clear correlation relationship between the two quantities was found.
Working conditions for fire fighters can be described according to the environment temperature and the incident radiant heat flux. Measurements for this study in buildings for fire fighting training have shown that fire fighters are typically exposed to radiant heat fluxes of between 5 and 10 kWm(-2) during this kind of exercise. The heat load can nevertheless be much higher. In one case, 42 kWm(-2) was measured. The temperatures reached between 100 and 190 degrees C at 1 m above ground, going up to 278 degrees C in one case. Human trials have been performed with 17 fire fighters. After exercises (about 15 min) in a heated room, the mean core temperature of the fire fighters rose by 0.6 degrees C with a surrounding temperature of 31 degrees C and 1.0 degrees C with 38 degrees C. The sweat production varied from 0.7 to 2.1 lh(-1); 16% to 45% of sweat remained in the clothing layers. During the exercises in the training buildings, a mean of 48 degrees C has been measured between fire fighters' clothing and workwear. These conditions lead to an increase of the relative humidity in all the jackets up to 100%. When the fire fighters came out of the fire, the humidity remained at this level in the PVC coated jackets while it was in some cases strongly reduced in breathable jackets.