Abstract: A method for operating an oxygen sensor arrangement senses the oxygen in a breathing loop of a breathing apparatus. The sensor arrangement includes a primary oxygen sensor to measure the oxygen in the breathing loop, a secondary oxygen sensor to measure the oxygen in the breathing loop, and a control arrangement to obtain measures from the oxygen sensor. A test channel arrangement provides a first gas having a first fraction of oxygen from a first gas supply to the primary oxygen sensor at a position adjacent to the primary oxygen sensor. A test valve arrangement opens and closes the flow of the first gas through the test channel arrangement. The control arrangement actuates the first test valve arrangement to provide an amount of the first gas to the primary oxygen sensor via the test channel arrangement and obtain measures from the primary and secondary oxygen sensors.

Abstract: An oxygen sensor arrangement is arranged to sense the oxygen in a breathing loop of a breathing apparatus. The sensor arrangement comprises at least one primary oxygen sensor arranged to operatively measure the oxygen in the breathing loop, and a control arrangement for obtaining measures from the oxygen sensor. A test channel arrangement is adapted to operatively provide a first gas having a first fraction of oxygen from a first supply to the primary oxygen sensor at a position adjacent to or directly adjacent to the primary oxygen sensor. A first test valve arrangement is arranged to operatively open and close the flow of the first gas through the test channel arrangement. The control arrangement is arranged to operatively actuate the first test valve arrangement so as to provide an amount of the first gas to the primary oxygen sensor via the test channel arrangement.

Abstract: The present invention relates to a mouth piece for a breathing apparatus, a breathing apparatus and a method for adjusting a valve trigger mechanism arranged on a mouth piece for a breathing apparatus. The mouth piece according to the present invention comprises a housing comprising a mouth piece breathing part opening for inhaling and exhaling a breathable gas. An inlet port for providing breathable gas into said mouth piece housing, the inlet port being in communication with valve means arranged to open or close said inlet port. The housing further comprises a first exit port for exhausting gas from said housing into a closed circuit flow channel and a second exit port for exhausting gas from said mouth piece housing into an ambient environment. Switch means for selectively directing said exhaust gas between said first exit port and said second exit port to change the mouth piece between open circuit breathing and closed circuit breathing.