Today I came across the word "deflagration" - (noun form, naturally, of deflagrate - To burn or cause to burn with great heat and intense light - AHD). This prompted me to look up conflagration (A large destructive fire).

So - which one's bigger? I've always thought of conflagration as about as big as a fire can get, but perhaps I've just never come across a deflagration.

Does anyone actually use deflagration (I came across it in a fairly technical sense)? Is a deflagration not necessarily destructive, but a conflagration is, by definition?

Also noted that deflagrate exists, in both transitive and intransitive senses, but conflagrate seems to have burnt itself out over time.

From the definition it sounds like deflagration is more about intensity than size.

OED2 gives it as a Physics term, more in use in the 18th and 19th Cs.

1. trans. To cause to burn away with sudden evolution of flame and rapid, sharp combustion (e.g. a mixture of charcoal and nitre thrown into a red-hot crucible).
1727 Bailey vol. II, Deflagrate, to inkindle and burn off in a Crucible a Mixture of Salt or some mineral Body with a Sulphureous one. 1794 J. Hutton Philos. Light, etc. 208 When coal is deflagrated with nitre. 1876 S. Kens. Mus. Catal. No. 1369 The spark from this battery deflagrates a platinum wire a foot long.

2. intr. To burst into flame and burn away rapidly.