A measuring system and device (12), a reaction carrier (14) and a measuring method for measuring a concentration of gaseous and/or aerosol components of a gas mixture are provided. The reaction carrier includes flow channels (42) and a coding that is detectable by a position sensor (36) to position the reaction carrier flow channels. At least one flow channel defines a reaction chamber (46) in which optically detectable reaction material (48) is provided. A position sensor detects a relative position of the reaction carrier. A conveying device (28) moves the reaction carrier relative to gas connections (22, 24) of a gas-inlet channel (16) and a gas-outlet channel (16, 18) between a measuring position with gas connections via a first flow channel for flushing the gas inlet channel and gas connections via a second flow channel defining a reaction chamber, for measuring the component of the gas mixture.