Odour wheel – A new supporting tool for the assessment of odours in indoor environments

Abstract

The presence of unusual or unexpected odours in indoor environments often causes concern among occupants about potential health effects of exposure to chemical substances. Accurately describing an odour in order to determine appropriate measurement strategies can be challenging, highlighting the need for supporting tools. An odour wheel can help to describe the perceived odour using odour-descriptive words. By providing a standardised vocabulary, an odour wheel may improve communication between affected persons and indoor air consultants, combining information from sensory perception with the need for analytical measurements. The aim of this study was to develop an odour wheel for the description of odours in indoor air. A literature review was conducted to identify odour-active substances and corresponding odour-descriptive words most commonly reported in indoor environments. These substances were prioritised through a multi-stage process involving expert consultations. Based on these results, a preliminary odour wheel was created and applied in 21 rooms, where panellists used it to describe the present odour. The results were compared with chemical and chemical-sensory analysis, including GC-MS for identification and quantification of VOC, HPLC for aldehydes and ketones, as well as GC-MS-sniffing for explicit identification of odours and odour-active substances. A final validation was conducted in artificially scented rooms using defined substance mixtures. The final odour wheel includes 66 single substances, mainly comprising the chemical groups of aldehydes, aromatic compounds, terpenes and alcohols. The odour wheel can support communication between occupants and indoor air consultants, selection of appropriate measurement methods, and source identification in indoor environments. © 2026 The Authors.