Expert: Jayendra Upadhye - 1/28/2006

Question
This might not be in your field, but I know you Astonomers are really smart so here goes...
In the case of a fire, what essentially comes first--the smoke or the fire?

I know it may sound a little simple.

Answer
Hi Terell,
Depends on what you term as a "fire"!
1 - If the fire started as a case of arson, the "fire", meaning flames come first.
2 - If the "fire" starts accidentally ie from a cigarette butt, then since "fire" is normally defined as "burning with flames", it comes much later and the smouldering propagated by the butt, into the "burnable" material such as a mattress, say, will set off a lot of smoke first.

3 - This is true of all fires starting from smouldering stuff, where the material first is raised to red-heat (not a fire at all) and liberates ignitable fumes. once the fumes have built up a critical mass around the smouldering area, they "burst" into flame and ignite the rest of the stuff.

In Conclusion:-
If fire is defined as burning with flames, then in some cases the smoke or fumes come first as a result of some ignitable matter getting raised to red smouldering heat.
The flames come a bit later. In many cases the fire never starts, and the thing actually "burns" out.

However is dull red charring heat is defined as "fire", then almost always the fire comes first, smoke later.

smouldering red heat is normally associated with cigarette butts, and over heated electrical wiring, where the overloaded electrical conductor burns thru the insulating plastic covers and is exposed to ignitable matter that begins to smoulder and release fumes.

hope that suffices.
Jayen