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GC-IMS is no longer “just” an interesting technique for odour work – it is becoming the reference backbone for serious, defensible environmental odour analysis. Around the world, leading labs and consultants are quietly adding it to their toolbox and discovering how much more robust, fast and objective their odour assessments can become. GC-IMS (Gas Chromatography – Ion Mobility Spectrometry) delivers 2D separation, sub‑ppbv sensitivity and rugged, portable hardware that goes where the odour problem really is: at the stack, on the boundary, in the plant. With IMS operating at ambient pressure using a Tritium beta source (IAEA/EURATOM exempt, no licence required) and water-based reagent ions, you avoid vacuum systems, fragmentation and the associated dilution effects, while still obtaining direct, high‑quality VOC fingerprints you can correlate with sensory data.​

   For years, odour units have been accepted but often questioned by operators, regulators and neighbours because they lack chemical transparency. GC-IMS changes that equation by measuring real VOC fingerprints in gas samples at sub‑ppm level with orthogonal GC+IMS separation, providing high selectivity across a wide range of volatiles. The instruments are compact and rugged, can be integrated in mobile labs or vans with an on‑board nitrogen generator, and need only mains power on‑site. Instead of discussing “odour annoyance” in abstract terms, you can present two‑dimensional plots, peaks and fingerprints that clearly differentiate sources and operating conditions.​

   VDI/VDE 3518 Part 4 is a new technical guideline that defines standardized test procedures and test-gas mixtures for VOC detectors used in indoor air quality (IAQ) measurements. Titled "Multigas sensors – Standardized test instructions and test gases for VOC detectors for indoor air quality measurement" it was published in April 2025 under ICS 71.040.40. This 42-page guideline aims to ensure that VOC-detector measurements are comparable and reproducible across different sensor technologies and manufacturers.

   The guideline is primarily aimed at manufacturers of VOC detectors and multi-gas sensors, testing laboratories, certification bodies, and experts in indoor air hygiene and building services engineering. It provides a framework for evaluating sensor performance, including sensitivity, selectivity, response time, and long-term stability. By defining standardized environmental conditions, gas mixture compositions, and test sequences, VDI/VDE 3518 Part 4 establishes a methodology designed to enable more reliable assessments of indoor air quality. Does it succeed? Read on to find out.