How to use a flue gas analyzer

Written by joshua smyth
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How to use a flue gas analyzer
Badly maintained boilers will release more pollutants through their flues. (gas flue image by Alison Bowden from

A chimney flue carries the exhaust from a boiler or fireplace up and out of a building. The exhaust is made up of the byproducts of the combustion that occurs when oil or gas is mixed with air and ignited in the boiler. A flue gas analyzer takes a sample of these gases, and analyses their chemical composition. This tracks whether a boiler is running at peak efficiency, or whether it is releasing high levels of pollutants like carbon monoxide or sulphur. Although each flue gas analyzer works slightly differently, the basic principles are the same.

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  • Flue gas analyzer

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  1. 1

    Consult the analyzer's manual for specific instructions. Some analyzers will require you to heat their probes before use, or to turn on a "Peltier Cooler" that chills the end of the probe enough to condense the gases that come into contact with it.

  2. 2

    Put batteries into your analyzer, and turn it on.

  3. 3

    Insert the probe into the air system before it enters the boiler. This will allow it to measure the temperature of the combustion air.

  4. 4

    Insert the flue gas analyzer's probe into the flue at a point just after the last heat exchanger, but before any draft-diverter vents or other sources of external air flow. This ensures that the analyzer only samples gases that have been through the boiler's combustion chamber, rather than gases contaminated by outside air.

  5. 5

    Pump flue gases into the probe using the small pump mounted on the hose connecting the probe to the analyzer.

  6. 6

    Look at the probe's screen to see the levels of different flue gases, measured in parts-per-million (PPM). If your analyzer has a built-in printer, you can print a hard copy immediately.

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