Irish people, it seems, were previously more tolerant of bad smells. Complaints about odours associated with industry have risen sharply, to judge from the most recent Environmental Protection Agency figures.
Dr John Reilly, laboratory manager with Bord na Mona Environmental Ltd, in Newbridge, Co Kildare, has no doubt that odour is becoming a big environmental and planning issue.
The EPA figures make his case. A total of 328 companies in the Republic in 1998 were subject to monitoring of their air emissions and discharges into water during 1998 as they operated under the Integrated Pollution Control licensing system.
Some 78 per cent of the 1,897 public complaints about these industries related to odour (the next biggest complaint category was noise, at 13 per cent). Odour complaints almost doubled on the previous year.
Increased urbanisation, with people living nearer factories, and intensification of the livestock slaughtering and rendering sector mean tolerance of bad odours is at a low level. Industry's environmental performance is being measured to a large extent on its odour control performance.
Putting a measure on odours becomes necessary to determine if a complaint is justified and to evaluate the success of a company in meeting planning conditions. Against that background, Bord na Mona Environmental Ltd built Ireland's first purpose-built olfactometry laboratory.
The company, which came into being in 1991, designs and makes pollution abatement products for municipal authorities and industry. It also provides an environmental consultancy service.
Bad odours do not necessarily mean toxic emissions. In Ireland, there is a large concentration of food industries which can give rise to nuisance odours.
Quantifying odours involves taking 50 litres of air into a special bag made of inert material which does not interact with the odour.
What compounds are causing an odour can be determined by drawing a sample into a "sorbent tube", combining gas chromatography and mass spectrometry, which determines the constituents.
An olfactomat is used to determine odour quantity when combined with the verdicts of an "odour panel". It's a process meticulously operated under EU SEN standards.
The sample is presented to the panel which includes selected individuals with odour sensitivities shown to be within the same range when tested with a standard compound. This guarantees consistency of measurement. Out of 50 people evaluated in 1999, only three met this requirement, though a panel of at least six is required each time.
The olfactomat is essentially a series of valves with a number of dilution ports. Initially, samples are highly diluted by specially cleansed air and it is impossible to detect the odour. Dilution is reduced on a gradual basis. The threshold is determined when 50 per cent of the panel detects the odour. The dilution at that point is then converted by software calculation to odour units per cubic metre.
This is a clearly defined scientific measurement, says Dr Reilly. "In my estimation, it's no more subjective than a classic BOD (biological oxygen demand) screen to give an indication of the quality of water or waste water."
Once the threshold figure is determined, it is possible to make an odour dispersion model.
When local topographical details and meteorological data are factored in, an odour contour map emerges. It looks much like a weather map, with linked isobars showing points with the same dilution level. It indicates how an odour might be dispersed, e.g. from a stack. The plume may cause no problems close to a plant but may hit a village miles away.
With environmental impact statements on proposed developments, odour levels are evaluated on site in advance. When built, return visits determine operational performance.
Odours provoke wildly differing reactions. However, the combination of olfactomat and odour panellists means evaluating smells can be an exact science.