Teledyne GFC-7001E - Trace CO Analyzer - Manual (Page 210)

Calibration Procedures Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 210
9.7.1.2. Set O
2
Span Gas Concentration
Set the expected O
2
span gas concentration.
This should be equal to the percent concentration of the O
2
span gas of the selected reporting range (default
factory setting = 20.8%; the approximate O
2
content of ambient air).