Abstract: The invention relates to a method for determining small quantities of carbon monoxide and nitrogen oxides in gaseous mixtures containing oxygen with the aid of a sensor whose electrical resistance changes at a higher temperature with the carbon monoxide and nitrogen oxide concentrations. It makes use of the fact that, with suitable sensors, on the one hand the resistance-temperature curve of the one of the gases to be determined is clearly different from that of the reference mixture over a broad temperature range (gaseous mixture without the two gases to be determined) and, on the other hand, the resistance-temperature curves of the two gases to be determined approach one another in one part of this temperature range, or coincide, and maintain a clear distance from one another in another part of this temperature range.

Abstract: An ignition system comprising one of a glow plug, spark plug and glow attachment having metal or ceramic surfaces which are exposed to a fuel/air mixtuer, and are at least partially covered with a coating comprising at least one complex metal oxide obtained as a result of a reaction of a basic oxide selected from a group comprising oxides of Si, Y, La and Ce and mixed oxides of the above-mentioned oxides with Al.sub.2 O.sub.3, with at least one further oxide selected from a group comprising oxides of alkali and alkali earth metals.