What is FTIR?

FTIR stands for Fourier Transform Infrared spectroscopy. It is a powerful gas measurement technology for simultaneous measurements of multiple gases. The ability to detect and measure almost any gas, combined with the robustness and reliability of the technology, makes it ideal for a wide variety of applications, such as emissions monitoring, environmental research and gas analysis for occupational safety.


After reading this White Paper you will learn:

  • How is the IR spectrum used for gas quantification?
  • What is the performance of FTIR in emissions monitoring?
  • When should a Gasmet FTIR be calibrated?
  • What is the typical response time?
  • How many gases can be measured and analyzed at the same time?
  • Which gases can be measured by the Gasmet FTIR gas analyzers?

Download FTIR Technology White Paper

How FTIR works?

All molecules can be identified by their characteristic absorption spectrum because each molecule absorbs infrared radiation at its characteristic frequencies. Every molecular structure has a unique combination of atoms and therefore produces a unique spectrum when exposed to infrared light. Even molecules with the same number of atoms in different positions can be distinguished. The only exceptions are diatomic elements such as O2 and noble gases, which do not absorb in the IR. IR absorption spectrum can be considered a fingerprint unique to each molecule.

The infrared spectrum is a plot of infrared radiation-related quantities as a function of wavelength or wavenumber. According to Beer’s law, the absorption strength (peak height) is directly proportional to concentration, and this way the IR spectrum can be used to determine concentrations of gases in the sample.

Do you want to know more about FTIR or are you just interested to see the science behind the technology? Join our free webinar where we talk about what actually causes infrared absorption in molecules and how it can be used to identify and measure gases.

Want to know more? Check our crash course:

Difference between IR Technologies

  • Non-Dispersive IR instruments (NDIR) measure only separate wavelength bands, no information from other parts of the spectrum. Only one component can be analyzed from a single measurement and interference cannot be compensated.
  • Fourier Transform Infrared (FTIR) spectrometer measures all the IR wavelengths simultaneously and produces a full spectrum. All components can be analyzed from a single measurement and interferences are resolved.


Infrared Gas Analyzers

Gasmet manufactures portable FTIR gas analyzers and stationary FTIR emissions monitoring systems. An FTIR analyzer works by simultaneously scanning the entire infrared spectrum. Then, Calcmet software calculates the concentrations of each gas in the sample based on the characteristic absorption. All the gases in the sample can be measured simultaneously because the entire infrared spectrum is scanned at once. This allows for very quick multicomponent measurements and for compensation for any cross-interference.

As all gases are measured by scanning the same infrared spectrum, adding new compounds can be done easily in the software without requiring any changes to the hardware. The recorded spectra are also unaltered by the analysis performed on them and can therefore always be re-analyzed. This allows for traceable data and facilitates for instance retrospectively checking the measurements for new gases.

All this makes FTIR the ideal solution for a variety of applications where multiple gases need to be measured quickly, accurately and reliably.

Why Choose Fourier Transform Infrared Spectroscopy?

  • Multicomponent capability – measure multiple gases simultaneously
  • Adding new gases is easy – no need for hardware changes
  • FTIR emission monitoring systems are available with performance approvals (TÜV, MCERTS)
  • A portable FTIR analyzer allows you to take the lab to the site
  • Simple and low-cost calibration – Gasmet’s analyzers do not need any span or re-calibrations, only zero calibration with nitrogen needed


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