Modelling carbon monoxide transport and hazard from smouldering for building fire safety design analysis

Abstract

Smouldering produces massive toxic smoke and carbon monoxide (CO) that is responsible for the majority of fire deaths, but current building fire safety design rarely considers smouldering hazards. This work investigates the transport and hazards of CO from smouldering fire for the building performance-based design practice. The numerical model is firstly validated by reproducing two flat-scale fire experiments, revealing the characteristic surface temperature and CO yield of smouldering sources. The smouldering fire scenario is then designed in an atrium to review the evolution of CO concentration and its associated Available Safe Egress Time (ASET). Results show that a smouldering fire of the same burning rate as a flaming fire not only can provide a similar ASET, but also present a greater threat to occupants and rescue teams by forming a cold layer of lethal CO on the ground. Hence, the smouldering fire scenarios and their CO hazards should be considered in the performance-based design of building fire safety. Simulations also reveal that the smouldering fire can be more dangerous as the atrium height decreases, and ceiling ventilation is particularly effective in extracting CO emissions from smouldering fires.