A method of monitoring at least two people with external air supply

The invention relates to a method for monitoring at least two persons who carry out a time-limited activity with an external air supply, particularly respiratory protective carrier such as firemen, scuba divers, or the like, in which levels of the persons with breathing air supply supplying breathing apparatus, in particular compressed air cylinders are detected and a central office is transmitted to monitor before the persons go to its operating the persons transmit at arrival on site an the arrival signal indicating to the central station which signal the calculation of the time interval between the arrival time and the beginning of the removal of respiratory air from the breathing apparatus is used. To a method for monitoring at least two temporary work to the effect form with external air supply persons carrying out that with a relatively simple and compatible equipment technology, which relies in particular on already existing equipment, a high level of safety for the working in dangerous places people is ensured, it is provided that the residence time at the site according to the formula t = V is calculated, where t is the residence time of