A fire suppression system , comprising: a pressurized inert gas source , comprising a plurality of storage tanks (140a-d), configured to provide a first inert gas output ; an inert gas generator configured to provide a second inert gas output ; a distribution network connected with the pressurized inert gas source and the inert gas generator to distribute the first and second inert gas outputs; and a controller operatively connected with at least the distribution network to control how the respective first and second inert gas outputs are distributed in response to a fire threat signal; wherein the controller is configured to: initially release the first inert gas output from the pressurized inert gas source in response to the fire threat signal to reduce an oxygen concentration within a given volume zone (114a;114b) that receives the first inert gas output below a predetermined threshold; and subsequently release the second inert gas output from the inert gas generator to facilitate maintaining the oxygen concentration below the predetermined threshold; characterised in that initially releasing the first inert gas output includes sequentially releasing pressurized gas from selected ones of the plurality of storage tanks of the high pressure inert gas source to reduce the oxygen concentration below the predetermined threshold. a pressurized inert gas source , comprising a plurality of storage tanks (140a-d), configured to provide a first inert gas output ; an inert gas generator configured to provide a second inert gas output ; a distribution network connected with the pressurized inert gas source and the inert gas generator to distribute the first and second inert gas outputs; and a controller operatively connected with at least the distribution network to control how the respective first and second inert gas outputs are distributed in response to a fire threat signal; wherein the controller is configured to: initially release the first inert gas output from the pressurized inert gas source in response to the fire threat signal to reduce an oxygen concentration within a given volume zone (114a;114b) that receives the first inert gas output below a predetermined threshold; and subsequently release the second inert gas output from the inert gas generator to facilitate maintaining the oxygen concentration below the predetermined threshold; characterised in that initially releasing the first inert gas output includes sequentially releasing pressurized gas from selected ones of the plurality of storage tanks of the high pressure inert gas source to reduce the oxygen concentration below the predetermined threshold. initially release the first inert gas output from the pressurized inert gas source in response to the fire threat signal to reduce an oxygen concentration within a given volume zone (114a;114b) that receives the first inert gas output below a predetermined threshold; and subsequently release the second inert gas output from the inert gas generator to facilitate maintaining the oxygen concentration below the predetermined threshold; characterised in that initially releasing the first inert gas output includes sequentially releasing pressurized gas from selected ones of the plurality of storage tanks of the high pressure inert gas source to reduce the oxygen concentration below the predetermined threshold. <EOS>