A low-cost and open-source olfactometer to precisely deliver single odours and odour mixtures

Despite its profound influence on human emotion and memory, and its critical importance in animal behaviour, olfaction has historically been understudied compared to other sensory modalities. Contributing to this relative neglect may be challenges inherent to odour delivery: unlike visual or auditory stimuli, odorants must be vaporised, transported, and actively cleared, requiring specialised equipment and creating temporal delays and contamination risks. While commercial olfactometers provide reliable solutions, they can be expensive and, due to proprietary software, may be difficult to customise. Existing custom designs, though excellent, often require specialized technical skills and/or access to engineering workshops. Thus, to help widen access to well-controlled odour delivery, we developed a low-cost, fully open-source olfactometer that can be assembled without specialised facilities or engineering skills and customised according to experimental needs. Our design prioritises affordability, accessibility, and versatility while maintaining temporal precision and stimulus control across applications from rodent behaviour to human psychophysics. This methods articles provides full design specifications, assembly details, and behavioural validation across both rodents and humans with the aim of reducing barriers and enabling more laboratories to study this crucial sensory system.