Abstract: In a method and a device for measuring the concentration of particles present in a gas, in which a gas stream is guided past a UV light source, the particles are ionized and filtered out and the resulting ionic current is measured, the gas flow required is produced by thermal convection using an internal or external heat source. A suitable internal heat source in this context is, for example, the UV lamp (2) itself, which heats the gas via a radiation absorber (5). The elimination of a mechanical pump reduces the space requirement, power consumption and susceptibility to faults of the measuring arrangement.