THE INFLUENCE OF HIGH-ALTITUDE ON FIRE DETECTOR TEST FIRES

We have measured the pressure dependence of fires similar to those of the European standard fires at altitudes above sea level from 400m (97 0 mbar) to 3000m (710 mbar) in a mobile test room of reduced size (6 x 2.8 x 2.1 m). At all altitudes combustible parameters were kept const ant. We recorded standard parameters, in particular optical extinction m, the gamma-value of the standard ionization chamber and increase in temperature Delta T, as well as CO, CO2 and O-2 concentrations. With decreasing outside pressure fires develop more slowly. Our data show a dependence of burning rates on pressure as alpha p(alpha) where alpha approximate to 1.3. Whereas maxima of Delta T and change of CO2 conce ntration show no significant dependence on pressure, maxima of extinct ion m decrease by a factor of 2.7 +/- 0.2 (polyurethane foam fire) or 2.2 +/- 0.2 (n-heptane fire) with pressure decreasing from 970 to 710 mbar. At this maximum pressure change, decrease of 'smoke density' y i s smaller. However, m/y ratios remain constant trp to an altitude of 1 800 m. (C) 1997 Elsevier Science Ltd.