Aluminium Smelters

Challenging environments in aluminium production

Process monitoring and monitoring of emissions from aluminium smelters can be a challenge due to high concentrations of for example hydrogen fluoride (HF) and dust. The use of sampling systems in such environments requires a lot of maintenance and is therefore costly. Such systems can also be unreliable. OPSIS offers better options.


The OPSIS monitoring system can be used for several different tasks in an aluminium smelter.

1. Measurement with open light beams inside the pot rooms, near the pots. It provides monitoring of potential leaks from the pots of HF and other substances with high time resolution. It provides a valuable tool for monitoring both the production process and the work environment.

2. Measurement of emissions to the ambient air through the stack or duct. Here, the systems are normally used to monitor that emission limits are not exceeded, and to raise alarms if this still occurs.

3. Surveillance of fugitive emissions through the roof ventilation. By combining the average levels of pollutants up at the lanterns with flow measurements, the plant's direct emissions from the production halls can be calculated. This can be done to protect the environment and it can be a requirement from the licensing authority.

4. Background monitoring in the facility's surroundings. To protect residents and others around the facility, the OPSIS monitoring system can also be used to monitor the air quality outside the facility. The monitoring results can be used both for environmental reporting and to be able to raise alarms in the event of accidental releases of hazardous substances. The application is described in more detail on our web page on so-called fence-line monitoring.


The OPSIS monitoring systems are based on gas analysers that have short response times, are accurate, and require minimal maintenance. The monitoring takes place contact-free along light beams where gas molecules can absorb parts of the light. In process monitoring, light beams are usually sent along the pot rooms. When monitoring emissions, light beams are sent through the gas ducts that lead to the facility's stacks, or some of the flue gases are led into measurement cells through which the light is sent. Fugitive emissions can be monitored with light beams near the lanterns of the pot rooms.

The light is captured and transmitted via optical fibres to the analyser which measures the absorption and calculates the gas concentrations. The analyser can therefore easily be placed well protected from the strong magnetic fields.

A single analyser can measure several types of gases along several light paths. It provides a very cost-effective monitoring system. In addition to HF, the concentrations of many other types of gases can also be monitored, such as NOX, SO2, CO, and CO2.


There are multiple reasons for choosing OPSIS as supplier of systems for gas analysis. Among the key benefits of the methods and solutions offered by OPSIS are:

  • one system for all components
  • a single system can measure at several monitoring points
  • combines the benefits of the UV-DOAS, FTIR-DOAS, and TDL techniques
  • best performance according to QAL1 certification
  • longest calibration interval according to QAL1 certification
  • optional automatic QAL3 control
  • non-contact monitoring, no sampling
  • long maintenance interval
  • low energy consumption
  • gas calibration only once a year
  • thousands of systems installed worldwide
  • certified by, among others, German TÜV and under British MCERTS standards.


Annual Calibration

System 400 – One system, three solutions

System 400 – One System, Three Solutions – Cross-stack

System 400 – One System, Three Solutions – Fast-loop

System 400 – One System, Three Solutions – HWE

OPSIS Data Services

OPSIS Open-path DOAS

Contact Henrik T OPSIS 720X480pxl

Contact me if you want to know more about our systems for monitoring in aluminium smelters!