Abstract: There is provided an apparatus for monitoring a wearer of a breathing apparatus, comprising a pressure detecting device and a mobile monitoring unit. The pressure detecting device comprises a pressure transducer arranged to detect a pressure of a gas supply of the breathing apparatus; and a wireless transmitter arranged to wirelessly transmit a preset number of ON signals when it is determined that the pressure of the gas supply has exceeded a predetermined on threshold. The mobile monitoring unit is arranged to be attached to the wearer and comprises a motion sensor arranged to monitor the motion of the wearer; an alarm; and a wireless receiver arranged to receive signals wirelessly transmitted by the wireless transmitter of the pressure detecting device.