USE OF A TIME CONSTANT FOR DESIGNING A SMOKE CONTROL-SYSTEM IN CAR PARKS

The fire environment in thirty-six car parks of volumes varying from 2 ,000 m(3) to 50,000 m(3), ceiling heights of 3 m, 4 m and 5 m are simu lated using the fire zone model, CFAST version 2.0 developed at the Bu ilding and Fire Research Laboratory, NIST in U.S.A. The concept of usi ng the space volume as a criterion to determine the requirement of smo ke extraction system is reviewed. The concept of time constant in an a trium hall is proposed to be used in car parks and underground spaces. The empirical expression fitted by experimental data appearing in NFP A-92B is applied to calculate the time constant. This is then correlat ed with the smoke filling time for those thirty-six car parks with and without natural horizontal ceiling vents. Design of the smoke extract ion system for underground spaces is also studied.