“Establishing a secondary reference odourant can help us further validate assessor performance and strengthen our confidence in the panel as a whole.”
Alicia Tran
St. Croix Sensory – Canada
Laboratory Coordinator
In the world of odour measurement, sophisticated equipment and standardized methods are important, but the quality of the data ultimately depends on the people evaluating the samples.
Odour testing conducted according to standards such as EN 13725 relies on trained human assessors to measure odour concentration. Because odour perception can vary from person to person, laboratories must invest significant effort in assessor selection, qualification, training, and ongoing performance monitoring to ensure results remain accurate, repeatable, and defensible.
At St. Croix Sensory, maintaining assessor quality is a continuous process. Assessors are screened and qualified according to established industry standards, but training does not stop after qualification. Ongoing quality assurance activities help ensure assessors remain consistent and that odour panels continue to produce reliable results over time.
To further strengthen these efforts, St. Croix Sensory recently conducted a collaborative study between our laboratories in the United States and Canada examining the use of secondary reference odours for assessor training and quality assurance.
Led by Alicia Tran, Laboratory Coordinator for St. Croix Sensory Canada, the study evaluated the use of dimethyl sulfide (DMS) as a secondary reference odour for assessor development and panel performance monitoring. By comparing results across two independent laboratory locations, the study provided a unique opportunity to evaluate consistency between odour panels operating in different facilities and composed of different assessor groups.
The study was initiated to address an important question in odour measurement: does qualification with a single reference odourant fully represent an assessor’s ability to evaluate the complex odours encountered in real-world environments? While n-butanol is the standard reference odourant used for assessor selection and qualification under EN 13725, environmental odours are rarely composed of a single compound. Instead, they are complex mixtures containing numerous odourants with different chemical and sensory characteristics. Because individual sensitivity to specific odourants can vary, there has long been interest in understanding whether assessors who meet qualification requirements using n-butanol demonstrate similar sensitivity to other compounds commonly encountered in environmental odour assessments.
The study found that trained and qualified assessors were able to detect and evaluate secondary reference odourants, and that panel performance remained consistent when results were evaluated at the group level. The results also suggest that incorporating secondary reference odourants into training and quality assurance programs can provide additional insight into assessor performance and further strengthen panel validation, helping laboratories maintain an even higher level of confidence in their odour measurements.
As odour measurement continues to play an increasingly important role in environmental compliance, community odour investigations, and research, the need for well-trained and highly qualified odour assessors remains as important as ever.
At St. Croix Sensory, we are committed to advancing odour science through continuous improvement, research, and quality assurance practices that help ensure every odour measurement is as reliable and consistent as possible. One of the unique advantages of operating laboratories in both the United States and Canada is the ability to conduct concurrent studies using two independent panels of trained odour assessors. This capability allows us to compare results across locations, verify panel consistency, and further strengthen the quality, reproducibility, and defensibility of our data. By leveraging the expertise of multiple assessor groups, we can continue to enhance confidence in odour measurements and uphold the highest standards of scientific excellence for our clients and the industry.