Examination of performance of water mist fire suppression systems under ventilation conditions

This paper describes water mist fire suppression effectiveness under various ventilation conditions. The full-scale fire test series were conducted in an empty enclosure and in a simulated machinery space. Fire scenarios in the tests included small and large pool fires, spray fires and wood crib fires that were placed at different locations within the compartment. The ventilation conditions varied from no ventilation, natural ventilation to forced ventilation. A single-fluid/high pressure and a twin-fluid/low pressure water mist systems were used, respectively, in the tests. The test results showed that water mist suppression effectiveness was dependent on ventilation rates, fire size, type and location in the compartment as well as the characteristics of the water mist system used. During tests, both single- and twin-fluid water mist systems effectively extinguished fires under natural ventilation. Under forced ventilation, however, water mist fire suppression effectiveness was substantially reduced due to the strong mass exchange between the room and its surroundings.