Effectiveness of High-Capacity Smoke Exhaust in Large Spaces

摘要

The qualities of the smoke layer can be estimated to assess the cost-effectiveness of the smoke management system for an atrium. Current codes in many countries require that the smoke layer be maintained above the highest means of egress in an atrium. The smoke exhaust capacity needed to maintain the smoke layer above the highest level of the means of egress within the atrium can be substantial if that level is near the top of a tall atrium. However, air entrained into the plume between the top of the burning fuel package and the underside of the smoke layer dilutes the smoke. For the case of a large clear height, the amount of dilution is substantial to moderate the hazard associated with the smoke layer. A first order analysis is described in this paper to estimate the properties of the smoke layer, including concentration of gas species, visibility reduction and temperature. In some cases, the visibility may 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 kg/sec in an atrium, the hazard associated with the smoke layer temperature and CO concentration is modest for a wide range of fuels.