The smoldering point is the lowest temperature, at which a solid substance delivers carbonization gases, so that developing carbonization gas/air mixtures can be inflamed by spark ignition.
according to VDI 2263
Inflammable carbonization gas/air mixtures develop from incomplete burn, from endothermically (warmth needing) or exothermic (warmth setting free) decompositions and also from the outgassing of volatile components.
In closed containers combustible mixtures can also be formed at temperatures below the smoldering point with some products during a longer period.
The evaluation of the smoldering point must include a comprehensive evaluation of the operationally relevant temperatures, residence times and local conditions.