Analyzer 1 for analyzing a fluid 3 containing at least one substance to be analyzed and at least one inflammable substance containing: a source of gas 9 to provide a flux of diluent gas, an injecting nozzle 11 for introducing samples of the fluid into the flux of diluent gas and for producing a gaseous flux, and a detector 7 for analyzing the gaseous flux, wherein: the source of gas is intended to deliver a flux of diluent gas containing a material capable of supporting the combustion of the inflammable substance, preferably to deliver a flux of air, the injection nozzle is configured so as to introduce into the diluent gas samples of the fluid such that the average volume fraction of the fluid in the gaseous flux is less than 1/2,000 and preferably less than 1/20,000, and the detector contains at least one microsensor for detecting the substance to be analyzed. Corresponding method.