To catch fire or burn strongly (of charcoal, firewood, etc.); to burn merrily or burn away — an intransitive verb (often written as 熾る but commonly in kana).
炭がよくおこって、囲炉裏が暖かくなった。
The charcoal burned well and the hearth became warm.
薪を少しずつ入れて火をおこした。
We added logs little by little until the fire caught.
火が熾る（おこる）音が夜の静けさに響いた。
The sound of the fire burning echoed through the quiet night.