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Odour nuisance is a subject that is arising throughout North America, however the quantification of odour is still a complex subject. It is important for industry to know that odour can be both quantified and qualified. Odour is inherently a complex pollutant because it is often caused by a mixture of chemical substances, and has subjective components associated with its perception by the human olfactory nerves. In order to understand the significance of the field observations, the odour measurements are defined by two methods:


Dilution-to-Threshold (D/T) in odour concentration measurements is a dilution ratio measured as the number of dilutions of odour filtered air needed to make the odourous ambient air "non-detectable". D/T is the numerical setting on the Nasal Ranger device, and can be represented by the following equation:


Many jurisdictions in North America define odour criteria using a relative-strength scale in terms of dilution-to-threshold (D/T) values, or alternatively, in terms of "odour units" (OUs). As a reference, 1 odour unit (or 1 OU) represents the diluted level where 50% of the population can begin to detect an odour

Odour Descriptors are the words that are universally associated with exemplars.  Examples of some odour descriptors are "fruity", "floral", "burnt", "rotten eggs", etc. The Character of an odour is important for distinguishing the generating sources.

Best Management Practices Plan (BMPP) are helpful to identify any potential odorous activities and/or processes. The BMPP can be used to create a written record of a facility's initiatives to manage odour nuisance impacts that may affect the surrounding community.

If you have any questions or concerns about the odour studies or require Trinity's assistance, please feel free to contact Suzy Sabanathan at (416) 391-2527 ext. 22.