Why GC-IMS is gaining ground in environmental odour monitoring

Why GC-IMS is becoming a valuable tool for odour monitoring

Odour complaints remain one of the most difficult challenges facing environmental operators and regulators. 

Whether the source is a wastewater treatment plant, landfill site, food processing facility or industrial installation, proving exactly where an odour originated—and why—can be far from straightforward.

For decades, dynamic olfactometry has been the accepted benchmark for measuring odour. 

Yet while it tells us how strong an odour is, it cannot reveal the chemical fingerprint behind it. 

As operators come under increasing pressure to understand and manage emissions more effectively, many are looking for analytical techniques that can provide a clearer picture of what is actually present in the air.

One technology attracting growing interest is Gas Chromatography–Ion Mobility Spectrometry (GC-IMS).

Adding chemistry to the odour conversation

Odour has traditionally been assessed through human perception. 

That remains important, but it can sometimes make discussions between operators, regulators and local communities difficult. 

Odour units alone do not explain what compounds are present or how emissions may change over time.

GC-IMS helps bridge that gap. By separating and identifying volatile organic compounds (VOCs) at very low concentrations, it produces a distinctive chemical fingerprint that can be linked to a specific source or process.

The result is a more detailed understanding of emissions. 

Rather than simply confirming that an odour exists, investigators can begin to identify patterns, compare operating conditions and distinguish between potential sources.

From the laboratory to the treatment works

One of the attractions of GC-IMS is that it is not confined to a laboratory environment. 

Modern systems are compact enough to be deployed in mobile laboratories and can be used directly at industrial sites, wastewater treatment plants and landfill facilities.

Researchers have already demonstrated the technology’s potential in real-world applications. 

Studies at wastewater treatment facilities have shown that different areas of a plant generate distinctive VOC fingerprints, making source identification significantly easier than relying on odour measurements alone.

The work also highlighted one of the technology’s key strengths: consistency. Unlike some electronic nose systems, which can suffer from sensor drift over time, GC-IMS provides stable analytical data with high sensitivity and relatively rapid analysis times.

Working alongside olfactometry

Importantly, GC-IMS is not being promoted as a replacement for dynamic olfactometry. Human perception remains central to odour assessment and is embedded within regulatory frameworks such as EN 13725.

Instead, the technology is increasingly being used to provide the chemical context behind panel-based measurements.

Researchers at Odournet in Barcelona have demonstrated how GC-IMS can be used to analyse VOCs captured in Nalophan sampling bags used for dynamic olfactometry. 

This allows analysts to compare odour measurements with the chemical composition of a sample and assess how emissions change during treatment processes or storage.

The approach can also help verify sample quality by identifying background contamination and monitoring the loss of volatile compounds over time.

Earlier warning of changing emissions

For plant operators, one of the most valuable aspects of GC-IMS may be its ability to detect subtle changes before they develop into larger problems.

By identifying variations in VOC concentrations at very low levels, the technology can provide early indications of process upsets, treatment inefficiencies or emerging odour issues. 

This creates opportunities for corrective action before complaints arise or compliance limits are approached.

The same analytical capability can support investigations into occupational exposure, helping organisations better understand the volatile compounds encountered by operators, sampling staff and odour panellists.

Supporting the next generation of monitoring technologies

The growing interest in GC-IMS extends beyond odour monitoring alone.

Researchers at ENEA in Italy are investigating its use as a reference technique for evaluating electronic nose systems as part of work supporting the forthcoming IEEE P2520.1 standard. 

By providing reliable and traceable analytical data, GC-IMS could play an important role in validating sensor technologies intended for industrial and environmental monitoring applications.

As electronic noses continue to evolve, having a robust analytical benchmark against which their performance can be measured will become increasingly important.

A technology coming of age

For many years, GC-IMS was viewed as a promising analytical technique with niche applications. That perception is beginning to change.

Advances in instrument design, improved portability and growing experience in environmental monitoring are helping the technology move from specialist research projects into routine field applications. 

At the same time, the demand for more transparent and defensible odour assessments continues to grow.

Dynamic olfactometry remains the foundation of odour measurement, but there is increasing recognition that sensory data alone may not always provide the full picture. 

By combining rapid VOC analysis with detailed chemical fingerprinting, GC-IMS is emerging as a practical tool for organisations seeking a deeper understanding of odour emissions and the processes that generate them.