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The Science of Measuring Odour

Posted on 25th January 2018

We’ve previously covered exactly what causes things to smell, and some of the worst offenders for odour in the world. But how do we understand odours, and how do we combat them? How is odour measured? Can it even be measured accurately? As experts in odour abatement solutions, our team have the answers when it comes to the science of odours.

How is odour measured?

It’s difficult to be precise when measuring odour

In Europe, odour is measured with the European Odour Unit, OUe. Odours are measured via the human nose and are ranked on a scale of 0-6, with 0 being no odour and 6 being intolerable. Specially trained odour assessors are used to detect the strength of the odour and its concentration in the location in terms of odour units per meter cubed – OUe/m3.

Odour assessors are carefully selected by their exposure and sensitivity to n-Butanol, a chemical that is widely used as the industry standard for odour measurement. The assessors are screened as a panel to ensure accuracy in testing of the odour that needs to be measured, and each assessor must be screened at least 10 times to ensure consistency in their sensitivity results.

When it comes to measuring the odour in question, samples are collected in vacuum sealed containers of non-odorous materials (such as Teflon) and these are then tested by the assessors. Once the assessors have produced a reliable result, this is calculated into the meter cubed format to assess what kind of solution is needed to combat the offensive odour.

Fun fact: In the perfume industry, odour assessors are known as ‘noses’. Becoming a professional perfume ‘nose’ takes seven years of training and qualifications in chemistry!

Some odours are also measured for their hedonic tone. Hedonic tone assessments are used to calculate the physical and emotional reaction people have to certain smells. The scale is ranked from extremely unpleasant, to neutral, to extremely pleasant. It also assesses how tolerable an odour is. The FIDOL factors are sometimes used for hedonic tone assessments, which are: Frequency, Intensity, Duration, Offensiveness, Location. Understanding the impact an odour has on people can be very important to help develop the right abatement solutions that keep residents happy.

Some assessments also use an olfactometer for detecting and measuring odour alongside human judgements. Olfactometers are more commonly used for market research purposes or for understanding certain animal behaviour responses to odours, as opposed to industrial applications.

What do odour measurements tell us?

Odour measurements help with deciding the appropriate course of action for odour abatement. If an odour is measuring high on the scale, Environmental Officers will put orders in for action to be taken and the offending odour to be reduced to a level where it is not impacting local communities or the environment. Knowing how intense and concentrated the odour is allows us to devise an abatement solution that can efficiently deal with it in the quantities present.

We’ve installed odour abatement solutions for a number of industries including water treatment, ready meal products, poultry preparation, pork processing and municipal sack waste facilities. To find out more about our highly effective solutions, please head over to our case studies page for more information.

Need help with odour abatement at your site? Contact our team of experts today.

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