There are two main categories of clean air wood fires:
CONVECTION fires provide a more even heat by distributing warm air around the room, because hot air rises, the air in the room is warmed from the ceiling downwards. A convection fire is more suitable for a room or house with a standard ceiling height and where more even heat distribution is desired.
RADIANT fires heat quickly and if you sit close to them you can get warm even if the whole room has not had time to warm up. A radiant fire transfers about two thirds of its heat by radiating out and one third by convection. I radiant fire is more suitable for rooms with high ceilings.