A system adapted to calibrate a determination of information related to one or more gaseous analytes in a body of gas being delivered to an objective by a gas source, the system comprising: a partial pressure sensor that generates an output signal related to the partial pressure of the one or more gaseous analytes in the body of gas; a total pressure monitor that determines the total pressure of the body of gas; a partial pressure module that determines the partial pressure of the one or more gaseous analytes in the body of gas according to a partial pressure function, wherein the partial pressure function describes the partial pressure of the one or more gaseous analytes in the body of gas as a function of the output signal generated by the partial pressure sensor; and a calibration module that is adapted to calibrate the partial pressure module by determining the partial pressure function, wherein the calibration module is adapted to determine the partial pressure function based on (i) a plurality of samples of the output signal generated by the partial pressure sensor at a plurality of points in time during a calibration time period, (ii) a plurality of determinations of the total pressure of the body of gas made at substantially the same points in time at which the plurality of samples of the output signal were generated, and (iii) a target concentration of the one or more analytes in the body of gas during the calibration time period, wherein the calibration time period comprises a time period during which the body of gas is being delivered to the objective while the gas source is adapted to operate to keep the concentration of the one or more analytes in the body of gas substantially equal to the target concentration while the total pressure of the body of gas is changed. a partial pressure sensor that generates an output signal related to the partial pressure of the one or more gaseous analytes in the body of gas; a total pressure monitor that determines the total pressure of the body of gas; a partial pressure module that determines the partial pressure of the one or more gaseous analytes in the body of gas according to a partial pressure function, wherein the partial pressure function describes the partial pressure of the one or more gaseous analytes in the body of gas as a function of the output signal generated by the partial pressure sensor; and a calibration module that is adapted to calibrate the partial pressure module by determining the partial pressure function, wherein the calibration module is adapted to determine the partial pressure function based on (i) a plurality of samples of the output signal generated by the partial pressure sensor at a plurality of points in time during a calibration time period, (ii) a plurality of determinations of the total pressure of the body of gas made at substantially the same points in time at which the plurality of samples of the output signal were generated, and (iii) a target concentration of the one or more analytes in the body of gas during the calibration time period, wherein the calibration time period comprises a time period during which the body of gas is being delivered to the objective while the gas source is adapted to operate to keep the concentration of the one or more analytes in the body of gas substantially equal to the target concentration while the total pressure of the body of gas is changed.