| 摘要 |
PROBLEM TO BE SOLVED: To surely prevent dew formation without causing an exhaust gas temperature to fall to less than a dew-point temperature in a sensor region regardless of an installation environment temperature and the exhaust gas temperature, thereby to stabilize an output performance of an exhaust gas sensor and correctly detect the concentration of carbon monoxide and the like.SOLUTION: An extraction pipe 3 extending obliquely upward to the wall of an exhaust gas passage 2 from a combustion apparatus takes out a part of an exhaust gas that passes through the exhaust gas passage 2 via a take-out passage 6, and is folded back at an end part of this take-out part 6, and returned to the exhaust gas passage 2 via a return passage 7. An upward recessed part (a hollow hole of a sensor attachment cylinder 14) provided on the return passage 7 is provided with an exhaust gas sensor 4. The exhaust gas sensor 4 detects the concentration of carbon monoxide, carbon dioxide, oxygen or a nitrogen oxide in the exhaust gas, and includes a heater for heating the exhaust gas sensor 4 or the exhaust gas flowing into the exhaust gas sensor 4. |
