Experimental Study of Gas Cooling During Firefighting Operations

Abstract

Gas cooling is a technique used by firefighters to reduce the dangers posed by the hot smoke in enclosure fires and, to thereby approach a fire while keeping their escape route safe. The technique includes bursts of water from a fog nozzle producing small droplets into the hot gases. The purpose of this work was to experimentally investigate the effects of gas cooling. A total of 44 tests were conducted in an 1800 × 1200 × 1200 mm room with an added fire room sizing 1200 × 760 × 1200 mm. A gas burner with a RHR of approximately 90 kW was used as a heat source. Four different nozzles were used, differing in droplet size, flow, and spray pattern. Also, reach, number of bursts and open time of the nozzles varied between tests. In this paper, six of the test with the most important and pronounced results were used for comparison. Conclusions from the tests included that nozzles producing droplets with a median diameter of approximately 500 µm delivered in multiple short burst with time in between bursts kept as short as possible were most effective for gas cooling. However, overall in this experimental setup taking all droplets sizes into consideration, a single longer burst performed slightly better than several short bursts as a similar temperature reduction is achieved in 1/3rd of the time of 5 short bursts and gases are cooled over a larger part of the room. The volume of the smoke was not observed to change significantly due to gas cooling.