A combustion system, said combustion system including: a) a wood burner, said wood burner characterised by: i. a firebox, ii. a firebase at, or forming, the bottom of the firebox, iii. a primary combustion zone for pyrolysising and/or combusting a biomass fuel, iv. a first air supply means for supplying primary air into the firebox, v. a secondary combustion zone for combusting gases and/or particulate matter produced from the pyrolysis and/or combustion of the biomass fuel, vi. an exhaust flue, said exhaust flue including a lower portion which extends to a position adjacent said secondary combustion zone, b) said firebase being adapted to support a charcoal/reduction layer between the primary combustion zone and the secondary combustion zone, the arrangement and construction being such that the gases and/or particulate matter, produced from the pyrolysis and/or combustion of the biomass fuel in the primary combustion zone have to pass over, or through, said charcoal/reduction layer prior to entering the secondary combustion zone and/or the exhaust flue, c) a second air supply means for introducing secondary air into the firebox, from a position outside of the firebox, wherein said secondary combustion zone is partially or wholly surrounded by said primary combustion zone, and characterised in that the arrangement and construction being such that said secondary air passes through, and is heated by, the charcoal/reduction layer and the secondary combustion zone, as it is introduced into the firebox, and in that the second air supply means is in the form of one or more apertures formed in the firebase of the firebox below the charcoal/reduction layer, whereby said secondary air is introduced into the firebox via said one or more apertures. a) a wood burner, said wood burner characterised by: i. a firebox, ii. a firebase at, or forming, the bottom of the firebox, iii. a primary combustion zone for pyrolysising and/or combusting a biomass fuel, iv. a first air supply means for supplying primary air into the firebox, v. a secondary combustion zone for combusting gases and/or particulate matter produced from the pyrolysis and/or combustion of the biomass fuel, vi. an exhaust flue, said exhaust flue including a lower portion which extends to a position adjacent said secondary combustion zone, i. a firebox, ii. a firebase at, or forming, the bottom of the firebox, iii. a primary combustion zone for pyrolysising and/or combusting a biomass fuel, iv. a first air supply means for supplying primary air into the firebox, v. a secondary combustion zone for combusting gases and/or particulate matter produced from the pyrolysis and/or combustion of the biomass fuel, vi. an exhaust flue, said exhaust flue including a lower portion which extends to a position adjacent said secondary combustion zone, b) said firebase being adapted to support a charcoal/reduction layer between the primary combustion zone and the secondary combustion zone, the arrangement and construction being such that the gases and/or particulate matter, produced from the pyrolysis and/or combustion of the biomass fuel in the primary combustion zone have to pass over, or through, said charcoal/reduction layer prior to entering the secondary combustion zone and/or the exhaust flue, c) a second air supply means for introducing secondary air into the firebox, from a position outside of the firebox,