Smoldering ignition and emission dynamics of wood under low irradiation

Abstract

Wood is one of the longest‐standing and sustainable construction and building materials, and has gained a new renaissance for high‐rise buildings to achieve global carbon neutrality. However, wood can sustain both flaming and smoldering fires, and numerous timber structure fires have raised fire safety to be a public concern. This work investigates the smoldering ignition of wood blocks under long‐lasting low‐intensity irradiation and the robustness of smoldering fire after the removal of irradiation. We found a smoldering ignition map including three regimes, (i) no ignition, (ii) unsustained smoldering, and (iii) self‐sustained smoldering. The minimum irradiation for smoldering ignition of wood is about 5.5 kW/m2 after heating for hours. Without sufficient and in‐depth preheating, smoldering ignition cannot self‐sustain without irradiation. The criteria for self‐sustained smoldering on thick wood include the minimum surface temperature of 350 ± 20°C, the minimum smoldering front thickness of 30 ± 5 mm, and the minimum mass flux of 3.8 ± 0.4 g/m2 s before the irradiation is terminated. The CO/CO2 ratio of the smoldering wood under low irradiation varies between 0.1 and 0.2. This work helps evaluate the fire risk of wood materials and understand their burning behaviors under real fire scenarios.

Fire research for timber structures

“…In a paper on smouldering ignition of wood, three different regimes were identified: (i) no ignition, (ii) un‐sustained smouldering and (iii) self‐sustained smouldering 7 . In the experimental campaign on beech woods, minimum radiant heat flux for smouldering ignition was about 5.5 kW/m 2 after long time exposure.…”

“…In a paper on smouldering ignition of wood, three different regimes were identified: (i) no ignition, (ii) un-sustained smouldering and (iii) self-sustained smouldering. 7 In the experimental campaign on beech woods, minimum radiant heat flux for smouldering ignition was about 5.5 kW/m 2 after long time exposure. A criterion for selfsustained smouldering, when smouldering continuous without irradiation, was set to (i) a minimum surface temperature of 350 ± 20 C, (ii) a minimum smouldering front thickness of 30 ± 5 mm and (iii) a minimum mass flux of 3.8 ± 0.4 g/m 2 s.…”

Contemporary Fire Safety Engineering in Timber Structures: Challenges and Solutions

“…Timber can sustain both flaming and smoldering fires [55]. Smoldering is a slow, persistent, and flameless form of combustion.…”

“…Smoldering can be a structural hazard in timber structures [56]. Timber's smoldering and flaming dynamics have been extensively studied in recent years [51,55,57]. For example, Zhang et al [51] studied the smoldering-to-flaming transition on wood induced by glowing char cracks and crosswinds.…”

Experimental Design for the Propagation of Smoldering Fires in Corn Powder and Cornflour

“…Therefore, comprehensive knowledge of smoldering is essential to prevent facility accidents. Some materials are susceptible to smoldering hazards triggered by self-heating or by an external source during storage [5]. Some grains, such as corn, have characteristics that Eng 2023, 4 may develop a smoldering reaction due to their level of combustibility.…”