Odour Impact Assessment Services

The major factors relevant to perceived odour annoyances are:

• Frequency of the odour occurrence,
• Intensity (strength of the odour)
• Duration of exposure to the odour,
• Offensiveness (a mixture of odour concentration, odour intensity, odour character and hedonic tone),
• Receptor tolerance.

Using an air dispersion model, it is possible to predict the downwind odour concentrations on the basis of odour emission rates, topography and meteorological data. The results can be checked against odour impact criteria to derive an odour impact area. Within this area, it may be expected that residents or other receptors will experience some degree of odour annoyance.

Odour dispersion modelling (hyperlink too dispersion modelling heading below) provides a benchmark/yardstick for the prediction of odour impact from odour sources. It is best to be used when a comprehensive study is carried out and then the same methodology is used to compare the likelihood odour impact.

Odour Impact Assessment can provide an effective tool for the following purposes:

• Preparation of environmental management plans.
• Development of appropriate regional and local planning and development control instruments.
• Odour regulation.
• Determine level and cost of potential investment for odour abatement.

The procedure requires an estimation to be made of the total odour emissions from the facility in question, and the use of atmospheric dispersion modelling techniques to predict the level of exposure of odours in the surrounding community. By application of a suitable odour annoyance criterion, the area where annoyance (which may lead to complaints of nuisance) may occur can be determined. This information can be used to ratify odour annoyance complaints, predict the likely impact of new and existing facilities, and to evaluate control strategies in order to identify the most cost-effective solution for a particular activity.

Sampling of odour emissions at source is conducted using equipment and techniques fully compliant with the standard for olfactometry, EN13725:2003 and takes account of the Draft austrilian sampling standard AS4323.40 - Area source sampling. Samples can be collected from a range of sources, including stacks and ducts, liquid sources (e.g. open tanks), solid area sources (e.g. open biofilters, waste, composting windrows) and from within buildings. Tracer gas studies can be used to determine the mass volume flow from a volume source such as a building with open doorway.

Odour sampling types:

• Point Sampling: 60 l point sampling of odour sources with an outward flow velocity (i.e. stacks, ventilation fans, flares, etc.).
• Area sampling: of area odour sources (i.e. composting pile, waste water processing tanks, etc.) with a calibrated wind tunnel system or flux chamber.
• Sampling of area sources with low efflux velocities using a special area sampling device (i.e. biofilters, aerated composting piles, etc.).
• Odour Monitoring Ireland also provides services for collection of samples from high temperature sources using our out of stack dilution system. This system continuously records the temperature of the sample, relative humidity of the sample and dilution ratio as the sample is taken thereby providing advancement in older techniques. The critical flow orifice is located outside of stack conditions so temperature changes with this orifice are minimised. The sample point static pressure is also taken into account in the sample acquisition so as to minimise the generation of erroneous results.