CALIBRATION PROCEDURES Model 300E Carbon Monoxide Analyzer
Instruction Manual
124 P/N 04288 REV: A
7.1.1. Zero Air and Span Gas
To perform the following calibration you must have sources for Zero Air and Span
Gas available.
Zero Air
is similar in chemical composition to the Earth’s atmosphere but scrubbed
of all components that might affect the analyzers readings. Zero air should contain
less than 25 ppb of CO and other major interfering gases such as CO
2
and Water
Vapor. It should have a dew point of -5°C or less
Span Gas
is a gas specifically mixed to match the chemical composition of the type
of gas being measured at near full scale of the desired measurement range. It is
recommended that the span gas used have a concentration equal to 80% of the full
measurement range.
If Span Gas is sourced directly from a calibrated, pressurized tank, the gas mixture
should be CO mixed with Zero Air or N
2
at the required ratio.
NOTE
ALL calibration gasses should be EPA Protocol gasses or NIST traceable standards.
Table 7-1: NIST – Standard Reference Materials (SRM) for Carbon Monoxide
SRM # Type
Volume
(Liters @ STP)
Nominal Concentration
(PPM)
1680b CO in N2 870 500
1681b CO in N2 870 1000
2613 CO in Zero Air 870 18.1
2614 CO in Zero Air 870 43.0
Zero air generators that condition ambient air by drying and removal of pollutants
are available on the commercial market such as the T-API Model 701 Zero Air
Generator. We recommend this type of device for generating zero air.
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