Odour Assessment by Queensland and NSW Laboratories

Odour Assessment Testing  

All testing is carried out to the Australian Standard 'The Determination of Odour Concentration by Dynamic Olfactometry, (AS/NZS 4323.3:2001). Testing is completed on OdormatTM dynamic olfactometers, each with a dilution range of 4 to 262,000 to one, with better than 10% dilution accuracy. The use of mass flow controllers in these machines ensures maximum reliability and dilution accuracy and minimal risk of contamination.  

Odours can affect public amenity and the community’s quality of life. Within the community, there is a large range of reaction to odour. On the one hand there are people who are very sensitive to odour. This odour-sensitive sector of the population will react, often strongly, to odours that are barely noticeable to others, or will have an expectation of very low environmental odour levels. On the other hand there are others within the community (often because of their association with the odour-generating activity) who are more tolerant of higher odour levels. The bulk of the population lies between these two, being unaffected by low levels of odour and being prepared to accept certain levels of odour.  

Odours are the largest source of air pollution complaints to the Department’s of Environment and Conservation (NSW) Environment Line. Odour problems generally arise when:  

• an activity is not operating in accordance with best management practice
• odour has not been appropriately considered in the planning and approval of an activity
• new or expanded urban development occurs near an existing odour-generating activity
• an odour-generating activity is inappropriately located near residential development, or
• an existing activity changes technology or increases the size of its operations, and this increases odour- generating activities.  

Controlling and managing odour is difficult for consent authorities, regulators, industry and the wider community because:  

• odours may cause psychological or physiological effects
• the sensitivity to odours is variable
• odour emissions are variable
• the impact of odours can be subjective
• odour dispersion modelling is not an exact science
• odour emissions are difficult to monitor (creating difficulties in verifying performance).  

Odour Assessment      

• Level 1 is a simple screening-level technique based on generic parameters for the type of activity and site. It requires minimal data and uses simple equations designed to indicate the likely extent of any odour impact. It may be used to assess site suitability and odour mitigation measures for new or modified activities and is particularly suitable for smaller developments in sparsely populated areas such as a small broiler chicken farm located in a rural area with no existing or likely future sensitive receptors located nearby.  

• Level 2 is a screening-level dispersion modelling technique, using worst case input data (rather than site- specific data). It is more rigorous and provides a more realistic prediction of the extent of any odour impact than a Level 1 odour assessment. It may be used to assess site suitability and odour mitigation measures for new, modified or existing activities. For example, Level 2 odour assessment can be used to determine whether a proposed upgrade and expansion of a sewage treatment plant would result in odour impacts on local residents.  

• Level 3 is a refined-level dispersion modelling technique that uses site-specific input data. This is the most comprehensive and most realistic level of odour assessment available. It may be used to assess site suitability and odour mitigation measures for new, modified or existing activities. For example, Level 3 odour assessment using concentrations of pollutants measured at site emission sources could be undertaken to assess whether proposed mitigation strategies would be adequate to reduce odour impacts from a waste oil processing facility, the subject of long-term numerous complaints from neighbours.