Odour Impact Assessment Handbook

Glossary and Abbreviations

Acute odour effect: the effect due to short-term exposure to odours sufficiently intense to cause adverse effects.

Adaptation: the phenomena of reduced sensitivity to a stimulus after prolonged exposure. Unlike habituation this refers to a reduced physiological as opposed to psychological response to a stimuli.

Annoyance: (1) when used in relation to an odour's character or pleasantness, annoyance is akin to the hedonic rating of an odour's pleasantness. (2) When used in conjunction with population annoyance surveys, it is a function of the attitude and feelings of the community towards a source (or sources) of ongoing odour impacts.

Area Source: a surface-emitting source, which can be solid for example, the spreading of wastes, material stockpiles, surface of a biofilter, or liquid for example, storage lagoons, effluent treatment plant.

Assessor: somebody who participates in odour testing.

Delayed olfactometry: measurement of an odour with a time-lag between sampling and measurement. The odour sample is preserved in an appropriate container.

Detection Threshold: the point at which an increasing concentration of an odour sample becomes strong enough to produce a first sensation of odour in 50% of the people to whom the sample is presented. The measurement of odour concentration is based on determining the detection threshold. This is a laboratory-based test and should be conducted according to the EN13725 European standard. The odour concentration at the detection threshold is one odour unit (per cubic metre).

Diffuse Sources: sources with defined dimensions (mostly surface sources) which do not have a defined waste air flow, such as waste dumps, lagoons, fields after manure spreading, un-aerated compost piles.

Dilution factor: the dilution factor is the ratio between flow or volume after dilution and the flow or volume of the odorous gas.

Direct olfactometry: measurement of odour concentrations without any time-lag between the sampling (operation) and the measurements; equivalent to dynamic sampling or on-line olfactometry.

Dynamic dilution olfactometry (DDO): the general procedure used to establish the relative odour concentration of a gas sample. The method establishes the extent of clean air dilution required to reduce the odour strength to a level that is at the threshold of detection for a calibrated panel. The sampling of the raw gas, dilution and presentation to the panel is undertaken in a continuous manner. The backcalculated concentration of the undiluted gas sample (OUE/m3) represents the number of dilutions with odour-free air required to reduce the odour of the gas down to the detection threshold.

Dynamic olfactometer: a dynamic olfactometer delivers a flow of mixtures of odorous and neutral gas with known dilution factors in a common outlet.

Electronic nose (E-Nose): an electronic device that uses an array of solid-state sensors, or synthesized protein sensors, that respond to the presence of different chemical compounds. The resulting electronic signals are processed using neural network computing techniques to help produce a two-dimensional spectral pattern that is specific to a particular mix of chemical compounds. The aim is to create different spectral patterns that can identify/fingerprint specific types of odour character.

European Odour Unit OUE/m3: that amount of odorant(s) that, when evaporated into one cubic metre of neutral gas at standard conditions, elicits a physiological response from a panel (detection threshold) equivalent to that elicited by one European Reference Odour Mass (EROM), evaporated in 1 m3 of neutral gas at standard conditions. One EROM is equivalent to 123 μg n-butanol.

Exposure: the dose received by a receptor, determined by the strength (concentration or intensity), time (duration and frequency) of a particular character odour.

Fugitive Releases: unintentional emissions from, for example; flanges, valves, doors, windows; that is, points which are not designated or intended as release points.

Fugitive source: any type of odour emission that cannot be readily quantified or defined. This usually refers to such sources as leaks in pipes, flanges, pump seals or structures, openings in buildings, floor spills, occasional sources such as uncovered truck loads or releases from pressure relief valves, and leaks in seals on covered tanks.

Gas Chromatography: this analytical technique is a form of chromatography that separates and detects compounds by the rate in which they move through an inert or un-reactive carrier gas such as nitrogen, helium or carbon dioxide. The time taken (residence time) to move through the glass or metal tube called a column is used to determine the type of compound present within the sample.

Habituation: a psychological term used to describe the process of decreasing behavioural response after repeated exposure to a stimulus such as odour over a prolonged period of time. This phenomena is particularly noticeable in commercial and industrial settings where occupational exposures to strong odours are no longer found offensive or even noticed by operational staff, for example, rendering plants, livestock, sewage and food processing.

Hedonic Tone: a judgement of the relative pleasantness or unpleasantness of an odour made by assessors in an odour panel. A methodology is described in VDI 3882, part 2. Odours which are more unpleasant will have a negative hedonic score whilst odours that are less unpleasant will tend towards a positive score.

Hyposmia: partial inability to detect odours (compare with anosmia).

Intensity: an assessment of odour strength based on an initial perception. This perception strength will rapidly diminish with constant exposure. The relationship between odour intensity and odour concentration depends on the specific intensity of the chemical or mixture being detected. Assessments can be made using the German method VDI 3882.

Isopleth: a line on a map connecting places registering the same amount or ratio of some geographical or meteorological phenomenon or phenomena. Commonly used to illustrate the output of odour models.

Mass Spectrometry: this is an analytical technique used to identify the chemical composition of a compound. The technique determines particles of the same type from the principle that particles with the same mass and charge will move in the same path in a vacuum when subjected to the same electric and magnetic fields. This principle of determining electronic mass and ionic charge allows the chemical composition of a sample to be determined from a database of existing compounds or unknown compounds to be detected. Three basic components make up a mass spectrometer; an ion source, a mass analyser and a detector.

Neutral gas: air or nitrogen treated in such a way that it is odourless, and which, according to panel members, does not interfere with the odour under investigation.

Odorant: a substance which stimulates a human olfactory system so that an odour is perceived.

Odour (or Odor): organoleptic attribute perceptible by the olfactory organ on sniffing certain volatile substances [ISO 5492].

Odour abatement efficiency: the reduction of the odour concentration or the odour flow rate due to an abatement technique, expressed as a fraction (or percentage) of the odour concentration in or the odour flow rate of the untreated gas stream

Odour annoyance survey (Community survey): standard survey method used to quantify the extent of population annoyance in different sectors of a community as a result of industrial odour impacts.

Odour concentration: the number of odour units in one cubic metre of gas at standard conditions. Note: odour concentration has a non-linear relationship with odour intensity.

Odour detection: to become aware of the sensation (smell) resulting from stimulation of the olfactometry system.

Odour diary: the systematic recording by individuals of odour events over a period of time at a defined location (normally a residential dwelling), including the date, time, duration, character, strength and weather conditions associated with each odour event.

Odour dose-response: the relationship derived between population annoyance and predicted odour impact concentrations, where the former is quantified via an odour annoyance survey and the latter is determined using odour emission measurement and modelling techniques.

Odour emission: the number of odour units per second discharged from a specific source.

Odour flow rate: the odour flow rate is the quantity of European odour units which crosses a given surface divided by time. It is the product of the odour concentration cod, the outlet velocity v and the outlet area A or the product of the odour concentration cod and the pertinent volume flow rate V. Its unit is OUE/h (or OUE/min or OUE/s, respectively).

Odour intensity: the perceived strength of an odour as rated by individuals against a...