Flow Conditioning Recommendations for O2 and CO2 Analyzers


Our process, research, and academic customers frequently inquire as to our recommendations regarding conditioning a sample flow, before introduction into our process analyzers*.  In general, proper conditioning of your sample will preserve the life of the sensors and prevent error in your readings. These are our general recommendations:

  • Flow Rate – Process analyzers generally have a “bypass” installed to vent excess pressure to atmospheric pressure.  While this is our default configuration, this may not always be the case.  Each analyzer is customized to the needs of the application – an analyzer with a bypass installed will generally respond slower (by 5-60 seconds), but can accept higher flow rates without producing a pressure effect on the readings.
    • Analyzers with a bypass installed – these analyzers will see no pressure effect on the readings until at least 500 cc/min.  Even above that, the difference is statistically within the margin of error.  The increase in your readings at about 1000 cc/min will be about +1% of the concentration being measured; i.e. 85% Co2 will read about 85.8%
    • Analyzers with no bypass installed – these analyzers will see a pressure effect of about +3% on your readings at 1000 cc/min; i.e. 85% CO2 will read about 88%.
    • How do I know if I have a bypass? –  Please check with us if you are not sure and we can look up your specific analyzer.  Alternately, you can open the top of the analyzer and examine the plumbing arrangement.
    • Best Practice – If you are unsure of your flow rate, pass your gas flow through a flow meter before introduction to the analyzer.  Use a T-splitter if necessary to vent some of the flow to air, if that is acceptable for your application.
  • Particulates – our internal filter will remove particulates bigger than 0.45 microns; however, it is best to filter your sample prior to introduction to the analyzer.  This is the smallest pore size filter that we currently use, and is sufficient for most applications.  You can also add an additional filter onto the inlet of the analyzer as well, as these are much easier to replace.
  • Moisture – We recommend that your flow be <95% RH, non condensing.  We do offer drierite removal tubes to mitigate the moisture issue.  Also, our internal four layer PTFE filter will remove moisture, but this should be depended upon only as a “last resort”.
  • Temperature – less than 50 degrees C
  • Other contaminants –  Your sample should be free of solvents, and free of dioxides that could react with water to form acidic compounds (such as NO2 and SO2).

* Process analyzers include our Model 902P O2 CO2 analyzer, our Model 905P oxygen analyzer, our Model 906 Co2 analyzer, or our Model 200/200A oxygen analyzers.