Breathing gas supply apparatus

摘要

A breathing gas supply apparatus comprises a variable volume reservoir (30) from which gas is dispensable and includes a section (42) moveable proportional to variations in volume of a gas containing portion of the reservoir (30). A position sensor (40) is provided and is adapted to monitor the location of the section (42) throughout an operating range of volumes of the variable volume reservoir (30). The position sensor (40) preferably comprises a non-ionising radiation, for example optical radiation, emitter (52) and a complementary detector (54) arrangement co-operable with the section (42) so that the section (42) will detectably influence the radiation from the emitter (52) incident on the detector (54) dependent on its location.