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,