Empirical study on the influence of initial relative humidity on wood crib fire behavior in compartment under varied natural ventilation conditions.

This empirical study investigates the influence of initial relative humidity (RH) variations (35 % and 95 %) on key fire behavior parameters, specifically focusing on the fully developed stage, occurrences of flashover, and the temperature of the upper gas layer. Wooden cribs weighing 10 kg–40 kg are used as fuel in a compartment with three openings to establish different natural ventilation conditions. The experimental findings reveal that increasing the initial RH within the chamber leads to a delay in the onset of the fire growth phase. Furthermore, it induces two noticeable effects on the fully developed fire stage: a reduction in its duration by up to 50 % and a delay in its initiation by at least 30 s. While heightened initial RH does not prevent flashover, it effectively postpones its occurrence by a minimum of 40 s. Experiments with maximum fuel loads demonstrate negligible effects of increased RH on the maximum temperature, even under varying ventilation conditions. Conversely, lower fuel loads exhibit a significant decline in temperature with rising humidity, notably from 626 °C to 474 °C. The quantitative and qualitative insights derived from this study have considerable potential to inform the development of more effective fire suppression strategies in enclosed compartments. • Augmenting the initial relative humidity (RH) not only retards the initiation of the wood crib fire growth phase by an average duration of 30–60 s but also, while not precluding flashover, significantly defers its onset by an average of 45 s. • Higher initial RH reduces the fully developed stage duration by up to 50 %, delaying its initiation by at least 30 s. • Implementing humidity in firefighting strategies can effectively delay fire stages, offering crucial time for extinguishment in multi-compartment scenarios. [ABSTRACT FROM AUTHOR]