Possibility of using a time constant in fire codes for smoke management in atria

The concept of using a time constant, a parameter describing the smoke filling process including atrium geometry and design of the fire, is further reviewed. Time constants of 138 local atria were investigated. The smoke filling time required to fill 80% of the space volume of 69 atria to satisfy the criteria for applying the NFPA smoke filling equation was evaluated with a slow t2-fire. The two-layer zone model ASET was used to calculate the smoke filling time for all 138 atria. The time for the smoke front to reach the ceiling is included to modify the calculation. The time constant has to be considered with the maximum allowed population density at the atrium floor. Evacuation time required in each atrium was also simulated using building EXODUS. It is confirmed that time constant is a better parameter than space volume that is used in the current fire codes, and is thus recommended to the Authority for smoke management in atria.