Investigation of Effects of Enclosure Opening on Inert Gas Suppression System

Abstract

A fire suppression system is very important for securing lives, property, and businesses. There are different kinds of fire suppression systems. The occupancy type is a major determinant of the type of fire suppression system suitable for use. In homes whose occupants are majorly those in the risk group, the use of an inert gas fire extinguishing system seems reasonable since it leaves no residue or damage property after discharge. However, the effectiveness of an inert gas fire suppression system may be affected by some factors such as openings in buildings they protect. The fire suppression system extinguishes fire by reducing the level of oxygen in the apartment below 15.0% which is the design concentration of oxygen to extinguish a fire. This study investigates the effects of openings on the inert gas system. Previous studies have been done for closed enclosures where fire suppression was achieved. The effect of enclosure opening on inert gas systems was investigated by conducting a full-scale experiment using a compartment of volume 83.5 m3. The oxygen level was measured at locations close to the doors and the windows. A similar arrangement was simulated in Pyrosim/FDS to get a clear view of the filling process and more data/information, which help to analyse the opening effect. From the investigation, the opening size and height affected the inert gas fire suppression system by increasing the oxygen level in the enclosure when IG-541 was discharged into the room. However, for locations far from the opening, the oxygen level decreased to a concentration that will enable the inert gas agent to extinguish fire (below15.0%). Also, the concentration of oxygen increased rapidly after the discharge time when there was an opening in the building which implied that the openings reduced the holding time of the inert gas system. The increase in oxygen concentration was because of the loss of the fire extinguishing agent through the lower part of the opening and the inflow of oxygen from the surrounding through the upper layer of the opening. In conclusion, openings under investigation affected the inert gas system by reducing the holding time, however, fire extinguishment was achieved. Therefore, to increase the holding time, extended discharge is required.