Production of activated carbons are a growing industry, and understanding to the processes involved in their synthesis is key to developing a better product. Generally the first step in the synthesis of activated carbon is the carbonisation of a material. During carbonisation the material undergoes aromatisation, and heteroatoms are removed, resulting in a highly aromatic carbon material. The physical and chemical properties are dependent on the degree of carbonisation and elemental makeup, which may be determined by the carbonisation conditions. In this study, properties of carbon chars derived from poly(divinylbenzene) are examined. Carbonisation conditions including, temperature, hold time, and atmosphere are studied to determine how these influence the thermal stability, elemental composition, and surface area and pore volumes of the final material. Surface areas were dependent on reactor gas, for nitrogen the surface area decreased from 665 m2/g to <1 m2/g as did pore volumes from 0.553 cm3/g to <0.01 cm3/g at 500°C; however, when the char was produced under an argon atmosphere, surface area and pore volume increased to 119 m2/g and 0.179 cm3/g. It was hypothesised that the difference between chars were due to a reaction of the char with nitrogen, which hindered the development of pores. Nitrogen reaction products were detected via elemental analysis and gas chromatography-mass spectrometry. This study shows the importance of the atmosphere and other parameters on the chars derived from poly(divinylbenzene).