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Why \"air free\" CO?

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DaveC
DaveC Member Posts: 201
in THE MAIN WALL
I know how "air free" CO is calculated - divide the "ultimate" CO2 (for the fuel used) by the actual CO2 measured, then multiply that result times the CO measured - the number is always higher. In the flue it is usually 1.3 to 2 times higher. In a more diluted area it could be many times higher. Do you still use the "air free" CO value for measuring room levels, or only in the flue? If there was a slight Oxygen depletion in the room, let's say 19.5 % instead of the normal 20.9 %, the instrument may calculate an "air free" CO of about 400 ppm from an actual CO reading of 20 ppm. If the Oxygen depletion was even more extreme, the CO calculated would not be as alarming, no?

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  • Rudy
    Rudy Member Posts: 482
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    Air Free CO readings

    The only time you use the CO air free reading is for flue gas analysis. Most combustion analyzers don't even start calculating CO air free until the O2 reading gets down to around 14%.

    Actually, the diluted CO reading in a flue gas sample is a pretty meaningless number, only CO air free readings should be looked at.

    You do make an interesting point that in an O2 deprived room with CO as opposed to a normal 20.9% O2, the air free reading would improve (I never thought of it in that way!!) - guess that's why CO air free readings are only for flue gas samples.

  • Unknown
    Unknown
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    Jim you sure do come

    up with some interesting questions. Rudy gave you a good answer. My take on the question is this. I have a tester which test both oxygen and CO in the room so I can get a comparison. The tester also measures gas (nat or LP) and hydoygen sulfide. It is strictly a safety detection device. It can also be used for bar testing gas samples on leak investigation sites.
  • DaveC
    DaveC Member Posts: 201
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    Thanks, guys...

    With all the CO discussions here recently, I was wondering if anyone else was getting confused about actual CO and "air free" CO, and where each is valid to use. One of the combustion analyzers we use starts to calculate an "air free" CO once the Oxygen goes below 19 % approx., that's where I noticed the tremendous multiplier for the CO level.
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