Breathing apparatus and a method of controlling the breathing apparatus

A breathing apparatus comprising a self-contained breathing apparatus with a demand valve at the outlet, a filter-ventilation unit with at least one air filter and a fan and further comprising a head unit with an inner space for pressure-separated breathing of the user from the surrounding environment and with a one-way exhalation valve, wherein the self-contained breathing apparatus and the filter-ventilation unit are fluidly connected to the inner space of the head unit, wherein

• the filter-ventilation unit is by its outlet fluidly unidirectionally coupled to the inner space of the head unit and
• the filter-ventilation unit is by its outlet fluidly unidirectionally coupled to the outlet of the self-contained breathing apparatus,
• the self-contained breathing apparatus is by its outlet fluidly coupled to the inner space of the head unit;
• wherein
• the filter-ventilation unit is provided with means for generating a stream (S2) of filtered air, whose pressure (p15) at the outlet of the self-contained breathing apparatus (1) is greater that the value of the switching pressure (pS) of the demand valve,
• and, at the same time, the demand valve is provided with means for spontaneous automatic opening of the inlet of autonomous breathing gas when the pressure (p15) of the stream (S2) of the filtered air at the outlet (of the self-contained breathing apparatus drops below the value of the switching pressure (pS) of the demand valve.