Calibration gas delivery apparatus

A calibration gas delivery apparatus for delivering a selectively humidified calibration gas to a measurement probe, the apparatus comprising:

• a) a delivery conduit having a conduit inlet adapted to receive at least one carrier gas stream including an analyte and a conduit outlet for delivering a calibration gas stream;
• b) an injection unit having an intake in fluid communication with a reservoir and an outlet in fluid communication with the delivery conduit, the reservoir adapted to hold a humidificant in liquid form;
• and
• c) at least one vaporizer downstream of the outlet and upstream of the conduit outlet for converting the humidificant to vapor form and delivering a calibration gas including all of said at least one carrier gas, and humidificant vapor to the conduit outlet.

A method of generating a calibration gas including at least one analyte and at least one humidificant, the method comprising:

• a) supplying at least one carrier gas;
• b) providing the carrier gas with at least one analyte, each analyte being provided at known concentration in the carrier gas;
• c) adding humidity to the carrier gas flow, to give a desired humidity level;
• and
• d) supplying the carrier gas including the analyte and added humidity to measuring equipment for detecting the analyte to enable calibration of the measuring equipment.