Evaluating the Smoke Hazard from Fires in Large Spaces

Current codes in many countries require that the smoke layer be maintained a particular distance above the highest walking surface in an atrium. The smoke exhaust capacity to accomplish the required performance can be extraordinary, especially in a tall atrium with the upper floors open to the atrium. The effect of exposure to smoke is a function of the magnitude of the smoke signature, e.g. concentration of gas species, visibility reduction and temperature, and the exposure duration. Generally, the first smoke layer property that reaches a critical level is a reduction in visibility. The visibility can be reduced below 1 m even though the temperature rise and generation of toxic gases are relatively modest. However, with a smoke exhaust rate of 200 kgs, the hazard provided due to temperature rise and CO concentration in atria is modest for a wide range of fuels.