Self-extinction of timber

Abstract Self-extinction of timber after the removal of an external incident heat flux is necessary to ensure that structures with exposed wood do not contribute to a fire after the building contents are fully consumed. Two series of tests with solid wood and cross-laminated timber were conducted to study the conditions leading to self-extinction. The heat fluxes and heating duration were varied systematically. For each test, the evolution of the in-depth temperature distribution was measured using thermocouples while the mass loss rate was measured using a load cell. The experiments were allowed to reach a steady-state mass loss rate. The in-depth temperature gradient, which represents in-depth heat losses from the pyrolysis zone, was calculated from thermocouple measurements until it reached steady-state. As the external incident heat flux increases, the mass loss rate as well as the in-depth thermal gradient reach a steady-state value. Once the steady-state mass loss rate and temperature gradient were attained, the external heat flux was removed and the flame was allowed to extinguish. Over the entire range of heat fluxes (30–100 kW/m2) and heating periods used in the tests, and for all the wood types used, self-extinction was observed.