Determining the partial pressure of a gas, calibrating a pressure sensor

A method of determining the partial pressure of at least one gas in a mixture of gasses contained in a pressure vessel, the mixture being pressurised to a level which is above local atmospheric pressure, in which the method comprises the steps of:

• positioning a gas analysis sensor within the pressure vessel;
• exposing the sensor to the mixture of gasses at the pressure level found in the pressure vessel;
• operating the sensor to measure the actual partial pressure of the at least one gas in the mixture contained in the vessel;
• and
• periodically calibrating the sensor by directing a calibrating gas mixture to the sensor in the vessel, the calibrating gas mixture being breathable by a human being, wherein the calibration gas mixture comprises a known proportion of a calibration gas.

A method of determining the partial pressure of at least one gas in a mixture of gasses contained in a pressure vessel, the mixture being pressurised to a level which is above local atmospheric pressure, in which the method comprises the steps of:

• positioning a gas analysis sensor within the pressure vessel;
• exposing the sensor to the mixture of gasses at the pressure level found in the pressure vessel;
• operating the sensor to measure the actual partial pressure of the at least one gas in the mixture contained in the vessel;
• and
• periodically calibrating the sensor by directing a calibrating gas mixture to the sensor in the vessel, the calibrating gas mixture being breathable by a human being, in which the step of calibrating the sensor comprises:
• supplying a low point calibration gas mixture to the sensor comprising a known first proportion of a calibration gas;
• monitoring a partial pressure value of the calibration gas outputted by the sensor;
• comparing the partial pressure value of the calibration gas outputted by the sensor to the actual partial pressure value which the sensor should output for said proportion of calibration gas at the pressure in the pressure vessel at which the measurement is made;
• determining any deviation between said values;
• and
• calibrating the sensor to account for any such deviation.

A method

• positioning a gas analysis sensor within the pressure vessel;
• exposing the sensor to the mixture of gasses at the pressure level found in the pressure vessel;
• operating the sensor to measure the actual partial pressure of the at least one gas in the mixture contained in the vessel;
• and
• periodically calibrating the sensor by directing a calibrating gas mixture to the sensor in the vessel, the calibrating gas mixture being breathable by a human being, in which the step of calibrating the sensor comprises directing a pre-prepared calibration gas mixture to the sensor, said pre-prepared mixture comprising a determined proportion of a calibrating gas.

A method of determining the partial pressure of at least one gas in a mixture of gasses contained in a pressure vessel, the mixture being pressurised to a level which is above local atmospheric pressure, in which the method comprises the steps of:

• positioning a gas analysis sensor within the pressure vessel;
• exposing the sensor to the mixture of gasses at the pressure level found in the pressure vessel;
• operating the sensor to measure the actual partial pressure of the at least one gas in the mixture contained in the vessel;
• periodically calibrating the sensor by directing a calibrating gas mixture to the sensor in the vessel, the calibrating gas mixture being breathable by a human being;
• wherein the step of positioning the sensor within the vessel comprises locating the sensor within a container defining a sensor chamber, and arranging the sensor chamber so that it communicates with the mixture of gasses in the pressure vessel;
• and
• flooding the sensor chamber with the calibration gas mixture to expel vessel mixture from the sensor chamber.