In a limited-current type gas sensor which detects oxygen-containing gas contained in an exhaust gas of an internal combustion engine, the decomposition current value of water (H.sub.2O) may be detected, and existence of an abnormality of output characteristics of the sensor may be diagnosed based on its deviation from a reference decomposition current value of water corresponding to the concentration of water contained in the exhaust gas. A NOx sensor and a SOx sensor can also diagnose remarkable and minute abnormalities of output characteristics. In addition, the reference decomposition current value of water may be acquired based on the concentration of water detected by a separate humidity sensor or the decomposition current value of oxygen detected by the limited-current type gas sensor. The reference decomposition current value of water may be corrected based on a decomposition current value of oxygen detected during a fuel cut.

A gas detection device includes a temperature control part configured to control an amount of energization to a heater so that an impedance of an element part matches a target impedance, to thereby control a temperature of the heater. The temperature control part is configured to set a first target impedance as the target impedance while performing application voltage control for air-fuel ratio detection, and set a second target impedance as the target impedance while performing application voltage control for SOx detection.

The present invention identifies substances which suppress odors of sulfide compounds. Provided is a method for evaluating and/or selecting an agent for suppressing odors of sulfide compounds, the method comprising: adding a test substance and a sulfide compound to at least one olfactory receptor polypeptide selected from the group consisting of OR4S2 and polypeptides having an amino acid sequence identity of at least 80% to OR4S2; and measuring the response of the olfactory receptor polypeptide to the sulfide compound.

A gas detection device includes: an element portion; a voltage applying unit configured to apply a voltage across a first electrode and a second electrode on surfaces of a solid electrolyte; a current detecting unit configured to detect an output current flowing between the first electrode and the second electrode; and a measurement control unit. The measurement control unit acquires a parameter which has a correlation with a degree of change of the output current increasing as a concentration of sulfur oxides in an exhaust gas increases based on the output current, and performs determination of whether the concentration of sulfur oxides in the exhaust gas is equal to or higher than a predetermined value or detection of the concentration of sulfur oxides in the exhaust gas based on the acquired parameter.

A gas detector includes a measurement control section that controls a voltage application section, obtains an output current flowing between a first electrode and a second electrode of an electrochemical cell, and detects a concentration of sulfur oxides in exhaust gas based on the output current. The measurement control section uses a minimum value of the output current obtained by using a current detection section in a period in which lowering sweep is executed and in which an applied voltage is a voltage within a detection voltage range that is equal to or lower than a decomposition initiation voltage of sulfur oxides as a parameter used for detection of the concentration of sulfur oxides.

The present invention is provided with: a SOx purge control unit that executes catalyst regeneration processing that maintains the temperature of a NOx occlusion/reduction catalyst at a prescribed recovery temperature; a catalyst temperature estimation unit that estimates catalyst temperature on the basis of the amount of unburnt fuel contained in exhaust and of a catalyst heat generation amount; a second exhaust temperature sensor that is arranged further to an exhaust downstream side than the catalyst and that detects exhaust temperature; and a heat generation amount correction value setting unit that, during the execution of the catalyst regeneration processing, on the basis of an estimated catalyst temperature estimated by the catalyst temperature estimation unit and of an actual exhaust temperature detected by the second exhaust temperature sensor, obtains a heat generation amount correction value that is used to correct the heat generation amount of the catalyst.

A species-specific gas sensor and monitor comprising a light source, a sample enclosure or measurement chamber, an optical interface between the light source, the sample and the detection system, electronics that integrate the light source and the detection system, and computational components, such as an onboard microprocessor for calculation of the gas composition and communications between the sensor and the vehicle electronics. The species-specific gas sensor of the present invention can be used to target gases, such as nitric oxide (NO), nitrogen dioxide (NO.sub.2) ammonia (NH.sub.3), and sulfur dioxide (SO.sub.2) which are measurable in the UV spectrum.

A control apparatus for an internal combustion engine is provided. The control apparatus includes a temperature sensor and an electronic control unit. The temperature sensor is configured to detect the temperature of an exhaust gas control apparatus. The electronic control unit is configured to: estimate a sulfuric compound accumulation amount on the exhaust gas control apparatus; and when a specific condition in which the sulfuric compound accumulation amount is equal to or larger than a predetermined accumulation amount and the temperature of the exhaust gas control apparatus is equal to or higher than a predetermined temperature or more is satisfied, control an intake air amount adjuster such that an intake air amount when the specific condition is satisfied is increased as compared to the intake air amount when the specific condition is not satisfied in the same operation state.

A SOx concentration acquiring apparatus of an internal combustion engine of the invention acquires sensor currents as SOx concentration currents after a sensor voltage reaches an oxygen decreasing voltage in a reoxidation voltage decreasing control, acquires the sensor current as a base current when the sensor voltage is equal to or lower than the oxygen decreasing voltage in the reoxidation voltage decreasing control, acquires an integration value of differences between the base current and each of the SOx concentration currents, and acquires a SOx concentration of an exhaust gas discharged from an internal combustion engine on the basis of the integration value.