I just noticed that if you pour copious amounts liquid nitrogen over burning coal until all of the coal is cooled below -80 (for example), once the flow is removed and all the N2(l) has evapourated, the coal carries on burning. I'm not sure if this is intended, I just thought I might let everyone know in case it is ;D
That's cause there are pixels of fire left on the coal, so it will burn (not very realistic though)
Also, coal burns with the help of "life" variable.