Abstract: An enclosure (17) contains two ovens (18, 19) each containing a semiconductor metal oxide (SnO.sub.2 or NiO) sensor (13) previously activated using H.sub.2 S or SO.sub.2. The sensors (13) are heated to different temperatures the lower of which corresponds to a peak on the sensor conductivity curve characteristic of the gas. The signals produced are applied to a comparator (30). For many toxic gases this peak occurs at concentrations below their toxicity threshold in air.
September 29, 1982
Date of Patent:
December 4, 1984
Association pour la Recherche et la Developpement des Methodes et Processus Industriels (Armines)