The moment combustible gases ignite in response to a spark from the spark igniter.
Cone Calorimeter Testing
In a cone calorimeter test, a cone-shaped heater above the specimen applies radiant heat to the specimen surface to induce ignition. At the beginning of the test, the spark igniter continuously generates sparks while radiant heat is applied. Once ignition occurs, the spark igniter is removed. I plan to document the test in more detail in a future article; this note records only the moment of ignition.
Interpreting This GIF
As the surface exposed to radiant heat reaches a high temperature, it continuously releases gases. The more combustible these gases are, the more readily they can ignite. Once ignited, they are likely to continue burning.
Considering this particular phenomenon, one approach to improving a material’s flame retardancy is to suppress the generation of these combustible gases or encourage the formation of an inert gas layer.