Quantifying extended discharge rate of inert gas agents to increase hold time for protection of enclosures with openings

Abstract

The application of gas-fire-suppression systems encounters a challenge that oxygen concentration tends to return to the original value in post-discharge time if open vents are present in a protected enclosure. Extending discharge becomes necessary to maintain oxygen concentration to prevent a fire resurgence in this enclosure. Until now the extended discharge rate must be evaluated individually by full-scale tests and no international standards specify the requirements in extended discharge. In this study, a formula was proposed to calculate the extended discharge rate as a function of opening size. A series of tests were conducted to investigate the oxygen concentration against the opening size in an apartment, followed by numerical simulations to recreate these tests. Then the discharge was extended in the simulations. Results show that the oxygen concentration was maintained between 10.5 % and 12.9 % in the apartment excepted the location next to the open door if the proposed discharge rate was adopted in the extended discharge time. Thus, this study proposal a universal method to quantify the extended discharge rate for a protected enclosure with openings.