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Gas Analysis Probe Oxygen Analyzer

industrial flue gas control oxygen

Nitrogen oxides (NOx) are an unwelcome group of gases that are the byproduct of combustion. In industries where combustion is used for heat or power, high oxygen levels in exhaust flues or stacks can indicate increased NOx levels as well as poor fuel combustion.

To minimize NOx in industrial settings SST Sensing has introduced the GAP Gas Analysis Probe, an all-in-one oxygen sensor that can be used to monitor oxygen levels in flue gases.

How is NOx Produced?

NOx is the name for a group of gases including Nitric oxide (NO) and nitrogen dioxide (N20). Measured in parts-per-million, NOx gases are produced from the reaction of nitrogen and oxygen molecules in the air during high-temperature combustion. In the atmosphere, NOx gases contribute to "smog" and are considered greenhouse gases.

Results of Low Combustion Efficiency

Inefficient combustion results in increased NOx levels which are not only bad for the environment, but increase fuel costs.

According to SST

"Efficient control of the combustion process plays an important role in reducing NOx output, reducing wasted fuel costs, increased lifetime of the flue or stack, increased process efficiency and reduction in thermal loss. It is estimated that every 1 % reduction in excess oxygen translates to a reduction of 20% NOx output and a further 1% reduction in fuel costs (source: North American Manufacturing Handbook)".

Improving Combustion Efficiency

To lower NOx levels, the amount of oxygen gas remaining in the flue or stack after combustion needs to be accurately measured. This data can then be used as feedback to more precisely control the fuel used in the combustion process.

Industrial Oxygen Sensors

In choosing the correct oxygen sensor, process engineers take into account the response time, sensitivity to the target gas, repeatability of readings and long term stability, ease of maintenance, ease of calibration, lifetime of the sensor and ease of the installation and communication.

For 16 years SST has manufactured Zirconia-based oxygen sensors with a unique fail-safe measuring principle. These sensors are used widely in combustion efficiency processes, environment monitoring and on-board aircraft systems. Continuous investment in research and design have produced rugged sensors with enhanced accuracy, resistant against vibration and high resistance to corrosion providing sensors with long lifetimes and allowing the sensor to be used in the harshest environments. Response times of under 15 seconds and accuracy of better than 0.25%, provides industry leading sensors engineered to perform better and last longer.

Gas Analysis Probe Oxygen Analyzer

SST's newest design is the GAP - Gas Analysis Probe, an all-in-one solution for combustion efficiency control in flue gas temperatures up to 700°C (1,292°F). The sensor is an in-situ stainless steel probe that draws the gases across the sensor via the pitot effect. This method allows the sensor to be contained outside of the stack/vent wall which allows maintenance to be carried out without removal of the probe.


  • The sensor is designed to need only one span point calibration which can be made in fresh air (20.7% O2), or the external calibration port can also be used to inject instrument or calibration air to the sensor should be specific calibration points be requested.
  • The sensor head contains the electronics, cable gland connection, user replaceable sensor module. Removal of the head takes seconds and this also exposes the twin tubes which can easily be cleaned of any dust and soot.
  • Industry-standard 4-20mA outputs for oxygen concentration and pressure provide linear signals for process control.
  • Two relay outputs with one for control and one for fault conditions provides reliable set point control.
  • RS485 Modbus RTU provides remote communication and control of relay outputs as well as multi drop addressing and system configuration.
  • The front panel display is IP65 rated and has soft touch push buttons allowing system configuration, manual relay control and commissioning tests. The display provides a two line readout of O2%, ppO2, temperature, pressure, relay set points and states, plus any fault codes.

The GAP Gas Analysis Probe is an ideal solution for minimizing costs via accurate measurements, long service life, low maintenance, and simple operation. Click here for more information or to purchase.

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