Saturday, 11 June 2011

Will Pinkham Wood smell? Bet you didn't know there is a Standard EuroNose!

European Odour Unit: That amount of odorant(s) that, when evaporated into one cubic metre of neutral gas at standard conditions, elicits a physiological response ["what's that smell?"] from a panel (detection threshold), equivalent to that elicited by one 'European Reference Odour Mass' (EROM), evaporated in one cubic metre of neutral gas at standard conditions. (CEN TC264 Draft)

European Reference Odour Mass (EROM): The accepted reference value for the 'European Odour Unit', equal to a defined mass of a certified reference material. One EROM is equivalent to 123mg n-butanol (CAS 71-36-3) evaporated in one cubic metre of neutral gas. This produces a concentration of 0.040 μmol/mol. (CEN TC264 Draft)

"The techniques available to measure odours can be broadly divided into sensory and chemical techniques.

"Sensory techniques utilise human assessors to assess odour [and are far more sensitive than chemical technology techniques]. The most commonly applied sensory technique is olfactometry, which is used to measure the concentration of an odour in terms of 'European Odour Units' (ouE/m3).

"The advantage of sensory methods is that they provide a direct link to how odours are perceived by humans. This is particularly useful for studies that involve assessment of annoyance or nuisance, or indeed how effective odour control techniques are at mitigating such issues.

"The 'offensiveness' of the odour perceived by a receptor is a factor that will determine the likelihood of annoyance. More offensive odours cause annoyance at lower concentrations, while less offensive odours cause annoyance at higher concentrations. The range between the annoyance criteria applied for the most offensive and least offensive odours is typically in the region of a factor 10.

"For example, in the Netherlands:
  • the most stringent criterion is 0.5 ouE/m3 to 1 ouE/m3 (for extremely offensive odours generated from rendering operations), and 
  • the least stringent is around 8 to 10 ouE/m3 (for relatively pleasant odours generated by bakeries, etc.)."

More material is available on web sites of two odour consultancies, by clicking on the images above. [Notice that the cartoon eyes blink!]

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