Fire smoke movement and distribution in ventilation shafts

Abstract

Abstract Vertical shafts are common structures in buildings, which accelerate smoke spread in fires due to stack effect. In this study, fire smoke movement and distribution in a ventilation shaft were studied through analysing temperature distributions, velocity distributions, CO2 concentration distributions and pressure distributions. Four exhaust rates were discussed and compared. It was found that the status of gas flow at the bottom of the shaft was firstly disturbed when the exhaust fan was working. Then some eddies appeared. As the number of eddies was increased and eddies got enlarged, gas flow in the entire shaft was influenced from the bottom to the top. A high temperature area and a strong convection area appeared close to the open door which was located at the bottom of the shaft. When the exhaust fan was working, the high temperature area and the strong convection area were both controlled at lower positions. The CO2 concentration and the pressure in the shaft were negatively related to the exhaust rate, while the neutral pressure plane height was positively related to the exhaust rate.