The invention concerns a method for measuring gas transfer time inside an enclosed space, such as a blast furnace, which consists in injecting a gas, called tracer gas, in a point A or A' of the enclosed space, for example a nozzle, and in tapping in a point B of the same enclosed space the gas present therein, the point A or A' being different from point B; in detecting the presence of the tracer gas in the gas tapped in B, and deducing therefrom the time required by the tracer gas to travel from point A or A' to point B on the basis of the data supplied by the detection system. The method also consists in carrying out at least one in-situ measurement of the response time, that is a calibration, of the tapping system in B. The calibration consists in injecting at the tapping point, concerning the equipment to be calibrated, an amount of a predetermined gas and in measuring the time separating said injection and the detection of said gas in the tapping and detecting equipment. Various methods are described two of which use tapping pipes with coaxial tubes and one with a single tube pipe. In case a rare gas, such as helium, is used as tracer gas, the blow-down gas can be nitrogen and the calibrating gas can be a helium-nitrogen mixture.