A device for detecting sulfuryl fluoride, in which the gas specimen to be examined is subjected to pyrolysis with ensuing detection of a pyrolysis product, is to be improved for the sake of achieving a mobile, economical structure. To attain this object, in a preliminary tube (1) for pyrolysis, there is a chemical layer (5) of pyrophoric iron, and as an indicator system for the pyrolysis product, a test tube (2) for hydrogen fluoride is used.