we know that to occur fire needs to have temperature,fuel and oxigen
but on powder toy just 1x1 px fire explodes all fuels
program the reactions
example
if hygn temp = 200C
temperature = 1
if oxygen near to fuel hygn -> 10 <- oxyg
oxygen=1
if (temperature=1+oxygen=1)
replace fuel with fire(REACT)
add a option to activate or disable this because this needs more computation power
This would be impractical because then oxygen would be needed for all combustion reactions, and you would need a constant supply of it to actually sustain a fire. In real life, this is not needed because of the abundance of oxygen in our atmosphere. If you really wanted this feature, it could be included in a mod, but I don't really see the use of such a feature. Air in the simulation acts like our atmosphere and provides a constant source of oxidizer.
For oxygen burning by itself, this is also unrealistic, but I don't know if it's worth "fixing".