Does wood smell more pleasant when we can see the grain than when only the odour reaches us? Tests of building-material odours sometimes conceal their source. In a real room, however, the visible materials also contribute to the impression.
A study published by Katja Butter and colleagues in 2025 examined both emissions from wood and photographs of the materials. It investigated how odour intensity, pleasantness and familiarity varied with chemical concentration, composition and visual information. The broader issue was how to interpret odour-based assessments of wood building products and indoor air.
Five materials, eight odour conditions
Thirty-five people participated in Germany. After three failed to meet the criterion on a preliminary odour-identification test, 32 completed the experiment. Their ages ranged from 18 to 66.
The materials were pine, oak, pine OSB, poplar OSB and cork flooring. OSB is a board made by layering and bonding elongated wood strands. High and low concentrations were prepared for pine, oak and pine OSB, giving eight odour conditions in total.
Materials were placed in containers with controlled temperature and humidity, and their outgoing air was collected in bags. The volatile organic compounds, or VOCs, in the bag air were analysed, while an apparatus delivered the samples to participants’ noses at a constant flow. Each presentation lasted 2.5 seconds, and each sample could be smelled at most twice.
The same people assessed all eight odours in two sessions. For each odour, the researchers compared presentation with a matching material photograph against presentation with an unrelated number on screen. Order was controlled, and participants were not told that they were evaluating the same odours twice.
Photographs increased pleasantness and familiarity
Overall, odours were rated as more familiar and pleasant when a material photograph was present. However, when familiarity changes were examined separately for each odour and adjusted for multiple comparisons, only the high- and low-concentration pine samples retained clear differences. An equally strong effect was not established for every material.
Photographs also had a significant effect on pleasantness. However, there was no statistical evidence that the image effect differed by odour type. Differences between material-specific means cannot simply be interpreted as an effect exclusive to a particular material.
Perceived intensity did not change significantly with the presence of a photograph. The finding was not that images made odours seem weaker. Instead, seeing the source may change how an odour is received even at a similar perceived intensity.
Total chemical concentration alone cannot predict odour
Comparing chemical measurements and odour ratings did not reveal a simple rule that more total emissions meant a stronger, more unpleasant smell. In these samples, terpene-rich pine odours were rated most familiar and pleasant overall. Samples with larger proportions of aldehydes or acetic acid tended to receive lower ratings.
For example, high-concentration pine had more than six times the total VOC concentration of low-concentration pine OSB, yet their perceived intensities were similar. Their saturated aldehyde concentrations were also comparable, but pine smelled more pleasant. A number for one component cannot fully explain the impression of a mixture.
Within the same material, higher concentrations smelled stronger. Pleasantness, however, did not clearly change for pine or pine OSB, while it decreased at the higher oak concentration. The effect of concentration on impressions therefore also depended on the mixture’s composition.
What does this mean for evaluating wood?
The authors considered whether photographs made the source easier to understand, bringing experience and images associated with wood into the judgement. Pine’s pleasantness might relate to the widespread use of softwood in Germany and familiarity with terpene odours in everyday products. These experiences were not directly established as the cause of the observed effects.
The authors proposed that partially revealing wooden materials in real buildings might increase the familiarity and pleasantness of their odours. At the same time, they cautioned against equating laboratory ratings of intensity or pleasantness with building-material quality or the health implications of indoor air. They argued that regulatory assessment should emphasize VOC emissions rather than rely on subjective odour ratings.
However, the experiment measured impressions after brief smelling. Although participants were asked to imagine spending several hours each day in the air, they were not actually exposed for long periods, and symptoms or toxicity were not examined. The high-concentration pine sample was prepared so that some components exceeded indoor guide values referenced in the paper. Pleasantness cannot be treated as evidence of safety.
Acetic acid measurements were also limited by interactions with the sampling bags and by the analytical method. The participants’ region and culture, and the range of materials, were restricted. In rooms containing several building materials and furnishings, emissions and adsorption change the odour mixture, so the results for these samples cannot be transferred directly to living environments.
Summary
Impressions of wood odour were not determined solely by chemicals in the air. In this experiment, material photographs increased pleasantness and familiarity without clearly changing perceived intensity. Total chemical concentration alone also failed to predict intensity or pleasantness.
The study suggests that understanding comfort in wooden interiors requires considering both the chemical mixture and what people understand its smell to come from. Design proposals that reveal wood and chemical-based health assessments each require further investigation. This study cannot be used to dismiss symptoms associated with odours as imagined.
The research was funded by Germany’s Federal Ministry of Food and Agriculture through FNR, the agency concerned with renewable resources. The authors declared no known competing interests that could have influenced the reported work.
References
Butter, K., Hucke, C. I., Ohlmeyer, M., & van Thriel, C. (2025). The impact of visual context on the perception of wood odours. Building and Environment, 280, 113129. DOI: 10.1016/j.buildenv.2025.113129 / Full text. © 2025 The Authors. CC BY 4.0.
