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

Olfaction has historically been the neglected sense, despite its profound influence on human emotion and memory, and its critical importance for animal behaviours including foraging, mating, and parenting. Perhaps contributing to this neglect is the fact that olfactory research has been hindered by technical challenges inherent to odour delivery: unlike visual or auditory stimuli, odorants must be vaporized, transported, and actively cleared, requiring specialized equipment and creating temporal delays and contamination risks. While commercial olfactometers provide reliable solutions for odour delivery, they are expensive and, due to proprietary software, difficult to customize. Existing custom designs, though excellent, may also be costly and/or require access to engineering workshops. To widen access to controlled odour delivery and hopefully encourage more labs to undertake olfactory research, we developed a low-cost, fully open-source olfactometer system requiring no specialized workshops or extensive engineering expertise. Our design prioritizes affordability, accessibility, and versatility while maintaining temporal precision and stimulus control and supporting diverse applications from rodent behavioural studies to human psychophysical investigations. In this methods article, which includes design specifications and assembly instructions as well as validation data, we aim to lower barriers to olfactory research and enable more laboratories to explore this fundamental sensory modality.