Flow measurement system arranged for controlling a gas fireplace , the flow measurement system comprising: - a flow passage defined by at least one flow-defining wall , the flow passage being in fluid communication with the gas fireplace to be controlled and being adapted to convey exhaust gas from the gas fireplace, - a differential pressure pressostat , - a first gauge connector arranged in the flow passage and connected to a first pressure sensor in the differential pressure pressostat , which first pressure sensor is configured to measure a total pressure in a fluid flowing in the flow passage , when the system is in use, and - a second gauge connector arranged near the first gauge connector and connected to a second pressure sensor in the differential pressure pressostat , which second pressure sensor is configured to measure a static pressure in the fluid flowing in the flow passage , when the system is in use, wherein: - the differential pressure pressostat is configured to determine a dynamic pressure in the fluid flowing in the flow passage , when the system is in use, based on signals from the first and second pressure sensors and in response thereto provide an output signal to the gas fireplace , and characterized in that : - the second gauge connector is arranged within a space defined by a surrounding wall , the surrounding wall being a part of the at least one flow-defining wall , the surrounding wall having at least one opening facing towards the first gauge connector , the surrounding wall and the at least one opening being dimensioned and shaped so that, when the flow measurement system is in use: - the static pressure in the space is the same or substantially the same as around the first gauge connector , and - there is no or substantially no flow of fluid in the space, whereby formation of water droplets on the second gauge connector is prevented. - a flow passage defined by at least one flow-defining wall , the flow passage being in fluid communication with the gas fireplace to be controlled and being adapted to convey exhaust gas from the gas fireplace, - a differential pressure pressostat , - a first gauge connector arranged in the flow passage and connected to a first pressure sensor in the differential pressure pressostat , which first pressure sensor is configured to measure a total pressure in a fluid flowing in the flow passage , when the system is in use, and - a second gauge connector arranged near the first gauge connector and connected to a second pressure sensor in the differential pressure pressostat , which second pressure sensor is configured to measure a static pressure in the fluid flowing in the flow passage , when the system is in use, - the differential pressure pressostat is configured to determine a dynamic pressure in the fluid flowing in the flow passage , when the system is in use, based on signals from the first and second pressure sensors and in response thereto provide an output signal to the gas fireplace , and - the second gauge connector is arranged within a space defined by a surrounding wall , the surrounding wall being a part of the at least one flow-defining wall , the surrounding wall having at least one opening facing towards the first gauge connector , - the static pressure in the space is the same or substantially the same as around the first gauge connector , and - there is no or substantially no flow of fluid in the space, <EOS>