Abstract: Particle concentration is monitored in a gas stream, in particular rust particle concentration in the exhaust gas stream of an internal combustion engine. A sensor in the gas stream collects the particles that are monitored. The sensor is integrated as a capacitive element in an electromagnetic resonant circuit excited by an alternating voltage. The sensor includes a non-conducting base body and two electrodes spaced apart from each other. A characteristic value of the resonant circuit varying on the basis of the particle load of the sensor is determined as a reference value when the sensor is unloaded. The change in the characteristic value due to the particle load is determined relative to the reference value.

Abstract: NOx is generated by means of a plasma-enhanced method which, with the addition of H2-containing gas, reduces NOx to NH3 and uses the thus obtained NH3 as the reducing agent for an SCR catalyst for exhaust emission control. A plasma reactor is provided in the corresponding apparatus for performing the method.