NOVELTY - The method involves conveying exhaust gas stream (12) from a processing chamber (10) using vacuum pumping arrangements (11, 22). The exhaust gas is abated in an abatement region of an abatement device (14) i.e. burner. A cooling agent e.g. liquid (26), is injected in a downstream of the abatement region to cool the abated gases by phase change of the cooling agent, where a characteristic of the abated exhaust gas is sensed by sensors (28) and an amount of liquid introduced to a cooling region (24) is controlled according to the sensed characteristic.    USE - Method for treating an exhaust gas stream from a processing chamber during manufacturing components for semi-conductor wafers, flat panel displays and solar cells.    ADVANTAGE - The method enables injecting cooling agent in a downstream of the abatement region to cool the abated gases by phase change of the cooling agent without adding the cooling agent to the volume of the gas stream handled by a downstream apparatus such as a filtration apparatus or vacuum pumping arrangement, thus avoiding increase of capacity of the downstream apparatus to manage increased gas flow volume, and hence reducing the energy consumption of the pump and reducing the size of the vacuum pump. The combusted flammable substances are injected into the burner in the gas stream upstream of the vacuum pumping arrangement so that any spark generated in the burner cannot ignite the gas stream and does not damage the vacuum pumping arrangement. The combustion gases are cooled in the cooling region before entering the vacuum pumping arrangement so that the vacuum pumping is not heated excessively and does not require additional cooling.    DETAILED DESCRIPTION - The cooling agent injected in a downstream of the abatement region is a liquid such as water, nitrogen or carbon dioxide.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a system for treating exhaust gases from a processing chamber.    Processing chamber (10)    Vacuum pumping arrangements (11, 22)    Exhaust gas stream (12)    Abatement device (14)    Fuel gas (16)    Combustion gases (20)    Cooling region (24)    Liquid (26)    Sensors (28)    Control unit (29)