Gas detection for automotive pollution control

The detection of the gases produced by the cars becomes an important object ive for different applications as urban pollution control or for the develo pment of car exhaust devices. The use of gas sensors can contribute to reac h such objectives. At the moment, the performances of the gas sensors avail able on the market especially SnO2 sensors are often not sufficient to sati sfy these needs. The major Limitations are dependent on their poor selectiv ity and stability. Some examples of such problems are presented through fie ld experiments in both types of applications and some feasible improvements of the sensors are discussed. In urban pollution monitoring, it is necessa ry to take into account the irreversible action of SO2. The dual response t o oxidising or reducing gases is a difficult problem to solve, especially f or the NOx gases. Solutions with metallic filters above the sensing materia l are currently studied. In order to be able to use directly the sensors in the car exhausts, new types of sensors are developed mainly on the basis o f electrochemical devices. An example of such new sensor is exposed with ex perimental results obtained on car exhausts. (C) 1999 Elsevier Science S.A. All rights reserved.