Abstract: Exhaust gas discharged from an exhaust port is taken into an exhaust gas sampling unit together with the surrounding outside air. A leak detection mechanism, which detects the leakage of exhaust gas from a sampling port, includes a temperature sensor including an outside and an inside temperature sensors, and a temperature measuring instrument for measuring a temperature difference between inside and outside temperatures detected by the temperature sensor. A plurality of inside/outside paired temperature sensors is disposed in the circumferential direction of the sampling port. When a leak occurs, the temperature of the inside temperature sensors rises and the temperature difference between the inside and the outer and outside temperature sensors increases, and the temperature measuring instrument detects the leak. When a leak occurs in a portion of the circumferential direction, only the temperature difference of the portion where the leak occurs is increased, and the location of the leak is identified.

Abstract: A filter made of a sponge material having air permeability and elasticity is interposed between an exhaust port of an exhaust gas sampling unit and a sampling port to thereby close a gap between the exhaust port and the sampling port. In this state, when the exhaust gas sampling unit is suctioned at a constant flow rate, the exhaust gas and the outside air around the exhaust port are taken into the exhaust gas sampling unit from the sampling port. At this time, the flow rate of the outside air taken in through the filter is suppressed by the air-flow resistance of the filter, and therefore the total flow rate of the exhaust gas and the outside air taken into the exhaust gas sampling unit is caused to be less than the suction flow rate, thereby simply and reliably preventing the exhaust gas from leaking out.

Abstract: A filter made of a sponge material having air permeability and elasticity is interposed between an exhaust port of an exhaust gas sampling unit and a sampling port to thereby close a gap between the exhaust port and the sampling port. In this state, when the exhaust gas sampling unit is suctioned at a constant flow rate, the exhaust gas and the outside air around the exhaust port are taken into the exhaust gas sampling unit from the sampling port. At this time, the flow rate of the outside air taken in through the filter is suppressed by the air-flow resistance of the filter, and therefore the total flow rate of the exhaust gas and the outside air taken into the exhaust gas sampling unit is caused to be less than the suction flow rate, thereby simply and reliably preventing the exhaust gas from leaking out.

Abstract: Exhaust gas discharged from an exhaust port is taken into an exhaust gas sampling unit together with the surrounding outside air. A leak detection mechanism, which detects the leakage of exhaust gas from a sampling port, includes a temperature sensor including an outside and an inside temperature sensors, and a temperature measuring instrument for measuring a temperature difference between inside and outside temperatures detected by the temperature sensor. A plurality of inside/outside paired temperature sensors is disposed in the circumferential direction of the sampling port. When a leak occurs, the temperature of the inside temperature sensors rises and the temperature difference between the inside and the outer and outside temperature sensors increases, and the temperature measuring instrument detects the leak. When a leak occurs in a portion of the circumferential direction, only the temperature difference of the portion where the leak occurs is increased, and the location of the leak is identified.