Long-term, Low-temperature Ignition of Wood

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For over a century, researchers have debated whether or not wood exposed to long-term, low-temperature heat sources can exhibit spontaneous combustion. Vytenis Babrauskas, author of Ignition Handbook, argues that ignition is possible for wood building members exposed to temperatures as low as 77^oC (170^oF) for long time periods (months to years). Due to internal heating (self-heating), a reactive char forms under oxygen-deficient conditions and eventually ignites as oxygen enters newly-formed cracks. Examples that we may encounter in the field include wood floor/ceiling assemblies penetrated by steam/hot water supply pipes or ducts. For the sake of comparison, external heating applies to the ignition of wood exposed to higher temperatures of around 250^oC (482^oF) for periods no longer than a few hours. Most causes of fire probably fall under this category.

For the fire investigators and chief officers out there, have any of you determined that a fire was caused by self-heating or pyrophoric carbon? Conversely, does anybody think that long-term, low-temperature ignition of wood isn't possible? My knowledge is limited, but I understand that this topic is controversial in the fire investigation community. For more information, click the link below.

'Pyrophoric Carbon' and Long-term, Low-temperature Ignition of Wood