A compressor system comprising: a compression device including a variable speed drive coupled to a compressor having a fluid intake, a fluid output, and a sump, the compression device operable between a first speed and a second speed to produce a flow of compressed fluid at an output pressure from a flow of fluid at an intake pressure; a blowdown valve movable between a closed position and an open position in which at least a portion of the flow of compressed fluid passes through the blowdown valve to reduce the output pressure of the flow of compressed fluid; a pressure sensor positioned to measure a downstream pressure of the flow of compressed fluid; a timer operable to output a signal indicative of the passage of time; a controller operable to: move the blowdown valve to the open position, set the speed of the compression device to a low set point speed in response to a measured downstream pressure of the flow of compressed fluid in excess of a predetermined pressure; characterised by a sump pressure sensor positioned to measure a sump pressure within the sump; and by the controller then being operable to: reduce the speed of the compression device from the low set point speed to a third speed lower than the low set point speed in response to the passage of a predetermined length of time and reduce the speed of the compression device from the low set point speed to zero in response to a measured sump pressure below a predetermined sump pressure, wherein the low set point speed is lower than the first speed and the second speed. a compression device including a variable speed drive coupled to a compressor having a fluid intake, a fluid output, and a sump, the compression device operable between a first speed and a second speed to produce a flow of compressed fluid at an output pressure from a flow of fluid at an intake pressure; a blowdown valve movable between a closed position and an open position in which at least a portion of the flow of compressed fluid passes through the blowdown valve to reduce the output pressure of the flow of compressed fluid; a pressure sensor positioned to measure a downstream pressure of the flow of compressed fluid; a timer operable to output a signal indicative of the passage of time; a controller operable to: move the blowdown valve to the open position, set the speed of the compression device to a low set point speed in response to a measured downstream pressure of the flow of compressed fluid in excess of a predetermined pressure; characterised by move the blowdown valve to the open position, set the speed of the compression device to a low set point speed in response to a measured downstream pressure of the flow of compressed fluid in excess of a predetermined pressure; a sump pressure sensor positioned to measure a sump pressure within the sump; and by the controller then being operable to: reduce the speed of the compression device from the low set point speed to a third speed lower than the low set point speed in response to the passage of a predetermined length of time and reduce the speed of the compression device from the low set point speed to zero in response to a measured sump pressure below a predetermined sump pressure, wherein the low set point speed is lower than the first speed and the second speed. reduce the speed of the compression device from the low set point speed to a third speed lower than the low set point speed in response to the passage of a predetermined length of time and reduce the speed of the compression device from the low set point speed to zero in response to a measured sump pressure below a predetermined sump pressure, wherein the low set point speed is lower than the first speed and the second speed.