Spec Gases

While transfilling oxygen gas all manufacturers are required to use a paramagnetic oxygen analyzer to determine the identity and strength of the gas.  Prior to using the analyzer it must be calibrated to manufacturer’s requirements.  In order to calibrate these analyzers the manufacturers require the use of specified (spec) or calibration gases that will provide the analyzer with a benchmark to compare to. 

Spec gases should include a COA (Certificate of Analysis) from the supplier of the gas.  The COA should include the actual results of purity of the gas when analyzed by the supplier.  When introducing gas from the spec gas cylinder into the analyzer be sure to use a low pressure regulator that limits the flow of gas to less than 10 psi.   

The common analyzer brands that are used in the compressed gas industry are Servomex and Oxigraf.  The specific spec gas requirements for each analyzer are shown below.   

Servomex

Nitrogen certified:  This gas is used to calibrate and adjust the low (zero) setting on the analyzer.

Oxygen certified:  This gas is used to calibrate and adjust the high (span) setting on the analyzer.

Oxigraf

Oxygen mixture:  This gas is used to calibrate the analyzer.