Abstract: The invention relates to novel methods and to devices for a measuring and analysis apparatus that measures impurities and/or particles in a gas or air. In a particle separation step, target particles having predetermined particle properties are separated from remaining particles from a gas or gas mixture such as air or a liquid, in short a fluid, that contains a particle mixture, and the occurrence and/or frequency of said target particles is determined in a measuring chamber. The likewise novel cooling of the radiation sources required for measurement permits the use of such having high power, as is required for measuring few particles or the smallest impurities. A further novel expansion of the electrical measurement range allows small but also abundant particles and impurities to be measured. In addition, a novel interface simplifies the start-up of the apparatus.