ORTECH can assess the Odour Impacts

Odour Impact Assessments are becoming more common place as municipalities and land use planners struggle with development in proximity to facilities that emit odours.  If you need to conduct an Odour Impact Assessment, please contact Steve Thorndyke.

What is an Odour Impact Assessment?

After you have determined what your odours are and where they are originating from, you need to examine the sources that have the largest offsite impact.  That is where a detailed Odour Impact Assessment can offer the greatest value.  The Odour Impact Assessment utilizes a number of sets of information including:

  • odour emissions details and variances,
  • location of odours,
  • impact on neighbours or receptors,
  • weather conditions,
  • Land types or typography,
  • land use,
  • dispersion models, (where the odour travels),
  • other site specific variables.

Assessing the odour impact of an industrial, commercial or municipal facility is a complex process, and there are a number of techniques. ORTECH has developed a structured process including a variety of assessment tools such as:

  • odour dispersion modelling studies: To better evaluate the odour potential from facilities and process changes, ORTECH uses advanced dispersion models such as ISCST3/Screen3, ISCPrime and AERMOD. The models predict the maximum off-property odour concentrations, plotted as isopleths overlain on topographical maps of the surrounding area. Locations of community complaints can be plotted and correlated with modeled results. The frequency and severity of odour threshold exceedence in the community can be predicted to help industry with abatement planning.
  • odour exposure assessment by direct field inspection:  Point sources of odour emissions at a facility are defined as sources where the emissions are enclosed by stacks and vents, prior to release into the atmosphere. Conditions in Certificates of Approval (Air) and other air permits frequently require that compliance odour testing is carried out at such sources if emissions of odour are potentially significant or the testing may be required as a result of odour complaints.
  • real-time odour monitoring and exposure profiling: Odour emission rates can be estimated by collecting air samples and determining the odour threshold values (OTVs) using sensory evaluation techniques. Air samples are usually collected by the dilution sampling procedure, which minimizes the loss of odorants by adsorption, condensation or oxidation. For open sources, odour sampling might be conducted using a lung or flux chamber technique. OTVs are used in conjunction with volumetric flow rates to calculate odour emission rates from the source.
  • odour complaint analysis and community monitoring: When many emission points or fugitive sources contribute to community odour complaints, trained observers are deployed in a structured evaluation protocol throughout the community. Observers record the intensity and character of odours. The data from this assessment can be interpreted to determine potential sources and impact of the odour. The resulting data can also be used to confirm odour dispersion modelling results.


ORTECH routinely conducts point source emission testing programs for all types of sectors including rendering plants, sewage treatment plants, composting facilities, paint spray operations and the food processing industry. For these programs, a number of odour sampling procedures are available for use depending on the characteristics of the point source emissions such as the gas temperature, the presence of moisture in the gases and the expected odour concentration.

To learn more, please contact: