| Since odour intensity is considered one of the primary variables in determining odour problems, a variety of methods for measuring odour intensity have been developed. "To date, a human sniffing panel is the most reliable method of odour evaluation," says Sherry Perih, an Agricultural Engineer-in-Training.
Olfactometer. Odour samples, collected in special sampling bags, are taken to an olfactometry lab. In the lab, trained odour panellists, typically eight, smell samples from three sniffing ports. One of these ports contains the diluted odour sample, while the other two are non-odourous samples.
Each panellist declares his reaction to the odour sample as a "guess," "detection" or "recognition." Panellists then receive another set of three samples to smell. However, this next set presents the odour at a higher concentration (i.e., two to three times). This continues until there is recognition of the sample by the panellists. This results in an overall declaration that the sample contained x number of odour units, which is odour concentration.
Both the U of A in Edmonton and ARC in Vegreville have olfactometry labs.
Nasal Rangers and Odour School. Odour School is a training course conducted by St. Croix Sensory Inc., Stillwater, Minnesota. Nasal Rangers are used to measure odour intensity. This course prepares trainees in the field evaluation of ambient odours. The purpose of the training is to produce a qualified observer whose judgement of odours will be consistent and minimally affected by variable field conditions.
In May 2001, approximately 45 people from Alberta, Saskatchewan and Manitoba attended an Odour School. At the end of the program, the participants were awarded Nasal Ranger certificates.
The Nasal Rangers who participated in this study were calibrated relative to the five-point odour intensity referencing scale - the range of intensities presented by a five-point scale that represents the range of intensities of pig odour downwind from a pig production site.
Electronic nose. The electronic nose is a developing technology. Scientists studying the mechanism of how the smell process works in humans are trying to use electronics to mimic the processes involved. Sensor arrays emulate the different type of olfactory sensors found in the human nose. The sensor response results in specific patterns. These patterns are then compared to the responses of known sample standards to characterize the odour. |