Understanding the effect of char oxidation on wood temperature profiles for varying heating and oxygen conditions

Nicolás Correa, Juan Cuevas, Andrés Fuentes, José Luis Torero, Pedro Reszka

Research output: Contribution to journalArticlepeer-review


The use of mass timber framing as a sustainable material, particularly in high-rise buildings, requires detailed structural fire performance calculations. Thermal models describing only the solid phase are cost-effective alternatives to provide information to structural behavior models. Their accuracy depends on an adequate description of drying, pyrolysis, charring and eventually flaming phenomena. While in recent years there have been considerable contributions to the development of such models, there are still open questions. This work proposes a thermal model which incorporates char oxidation, describing both the kinetic- and diffusion-controlled regimes. The model was used to replicate two sets of experimental results which used standard fire calorimeters to study the ignition of thick wood specimens within a range of incident heat fluxes and oxygen concentrations, respectively. The model yields adequate temperature predictions in the early heating stages, but fails to replicate the behavior at later stages, when the effect of the surface combustion is noticeable. In terms of mass loss rates, a poorer performance is observed. To change from one oxidation regime to another, a Damköhler number is proposed, based on char oxidation reaction rates. It is found that for compartment fire conditions, char oxidation will mostly occur develop under diffusion-controlled conditions.

Original languageEnglish
Article number104049
JournalFire Safety Journal
StatePublished - Jan 2024
Externally publishedYes


  • Pyrolysis modeling
  • Structural fire behavior
  • Temperature profile
  • Wood heating


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