A respiration system, comprising: a pressure regulator comprising a housing, an inlet for connection to a pressurized gas comprising oxygen, and a first data communication system; wherein the first data communication system comprises a plurality of light transmitters as light sources (480a, 480b, 480c, 480d, 482a, 482b and 482c) at spaced positions that align with ports (486a, 486b, 486c, 486d, 488a, 488b and 488c) formed in the pressure regulator in the rearward surface of rearward extending section of the pressure regulator, when the pressure regulator is assembled, the system further comprising a respiration facepiece comprising a generally central front port, an interface with a pressure regulator interface port to which the pressure regulator is removably attachable, the pressure regulator interface comprising a second data communication system, wherein the second data communication system comprises a plurality of light guides (293a, 293b, 293c, 293d) that align with ports (290a, 290b, 290c, 290d, 292a, 292b and 292c) formed in the pressure regulator interface, wherein each of the plurality of light guides (293a, 293b, 293c, 293d) comprises a translucent polymeric tube, wherein upon attachment of the pressure regulator to the pressure regulator interface port ports (486a, 486b, 486c, 486d, 488a, 488b and 488c) of the pressure regulator align with ports (290a, 290b, 290c, 290d, 292a, 292b and 292c) of the pressure regulator interface, and thus each of the plurality of light transmitters (480a, 480b, 480c, 480d) being aligned to transmit light to a first end of one of the plurality of light guides (293a, 293b, 2 93c, 293d), at least one seal system to form a sealing engagement with the face of a user to encompass the nose and mouth of the user; wherein a sealing attachment is formed between the pressure regulator and the interface of the facepiece, an inspiration port in fluid connection with the pressure regulator interface and in fluid connection with the interior of the facepiece, and at least one display within a volume of the sealing engagement with the face of the user formed by the respiration facepiece that is within the field of view of the user, wherein the at least one display comprises a second end (293a', 293b', 293c', 293d') of at least one of the plurality of light guides (293a, 293b, 293c, 293d), the pressure regulator interface comprising the second data communication system to receive data from the first data communication system, when the sealed attachement between the pressure regulator and the pressure regulator interface is formed, to control the at least one display. a pressure regulator comprising a housing, an inlet for connection to a pressurized gas comprising oxygen, and a first data communication system; wherein the first data communication system comprises a plurality of light transmitters as light sources (480a, 480b, 480c, 480d, 482a, 482b and 482c) at spaced positions that align with ports (486a, 486b, 486c, 486d, 488a, 488b and 488c) formed in the pressure regulator in the rearward surface of rearward extending section of the pressure regulator, when the pressure regulator is assembled, the system further comprising a respiration facepiece comprising a generally central front port, an interface with a pressure regulator interface port to which the pressure regulator is removably attachable, the pressure regulator interface comprising a second data communication system, wherein the second data communication system comprises a plurality of light guides (293a, 293b, 293c, 293d) that align with ports (290a, 290b, 290c, 290d, 292a, 292b and 292c) formed in the pressure regulator interface, wherein each of the plurality of light guides (293a, 293b, 293c, 293d) comprises a translucent polymeric tube, the pressure regulator interface comprising a second data communication system, wherein the second data communication system comprises a plurality of light guides (293a, 293b, 293c, 293d) that align with ports (290a, 290b, 290c, 290d, 292a, 292b and 292c) formed in the pressure regulator interface, wherein each of the plurality of light guides (293a, 293b, 293c, 293d) comprises a translucent polymeric tube, wherein upon attachment of the pressure regulator to the pressure regulator interface port ports (486a, 486b, 486c, 486d, 488a, 488b and 488c) of the pressure regulator align with ports (290a, 290b, 290c, 290d, 292a, 292b and 292c) of the pressure regulator interface, and thus each of the plurality of light transmitters (480a, 480b, 480c, 480d) being aligned to transmit light to a first end of one of the plurality of light guides (293a, 293b, 2 93c, 293d), at least one seal system to form a sealing engagement with the face of a user to encompass the nose and mouth of the user; wherein a sealing attachment is formed between the pressure regulator and the interface of the facepiece, an inspiration port in fluid connection with the pressure regulator interface and in fluid connection with the interior of the facepiece, and at least one display within a volume of the sealing engagement with the face of the user formed by the respiration facepiece that is within the field of view of the user, wherein the at least one display comprises a second end (293a', 293b', 293c', 293d') of at least one of the plurality of light guides (293a, 293b, 293c, 293d),