Editing Autoignition temperature (section)

==Autoignition time equation==
The time <math>t_\text{ig}</math> it takes for a material to reach its autoignition temperature <math>T_\text{ig}</math> when exposed to a [[heat flux]] <math>q''</math> is given by the following equation:<ref>Principles of Fire Behavior. {{ISBN|0-8273-7732-0}}. 1998.</ref>

:<math>t_\text{ig} = \frac{\pi}{4} k \rho c \left [ \frac{T_\text{ig} - T_0}{q''} \right]^2, </math>

where ''k'' = [[thermal conductivity]], ''ρ'' = density, and ''c'' = [[specific heat capacity]] of the material of interest, <math>T_0</math> is the initial temperature of the material (or the temperature of the bulk material).