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What You Should Know About Hedonic Tone

What You Should Know About Hedonic Tone

Hedonic tone odour assessments rate the level of pleasure, or displeasure, of an odour


In brief, a hedonic tone odour assessment is a subjective testing process. It measures the level of pleasure, or displeasure, that specific odours create when they come into contact with the human nose. We then give a ‘score’ to each odour.

Our highly trained odour panel generates the scores.

At Silsoe Odours, our trained panel of assessors carry out hedonic tone odour assessments.

The Silsoe Odours assessor panels are selected and screened to BSEN13725.


The percieved hedonic tone score of an odour ranges from very unpleasant (-4) to very pleasant (+4).

Perceived Hedonic Tone Score from Very Unpleasant (-4) to Very Pleasant (+4)

Examples of odours which might receive a very pleasant score include bakery smells (+3.53) and chocolate (+2.78). On the other hand, odours you could expect to receive a very unpleasant score could include burnt rubber (-3.01) and cat urine (-3.64).

Pleasant and unpleasant odorants


The results of hedonic tone odour assessments give you valuable information. When you understand how people are likely to perceive the odours produced by your processes, you can manage those odours effectively.

Effective Design and Planning

If you are aware of the hedonic definition of your odour emissions, you can plan appropriately in relation to your local environment. For obvious reasons, odours registering low on the hedonic tone scale will often cause complaints. Knowing this early in your design or operating process allows you to introduce effective solutions. You could use abatement equipment, effective odour management practices or a combination of the two.

Prevent and Manage Complaints

Hedonic tone odour assessments can help you prevent and manage odour complaints. Many industrial odours can be tolerated in relatively high concentrations, as long as they don’t impact negatively on those in the immediate vicinity. However, odours which register low on the hedonic tone scale are likely to cause complaints. This is because they impact the quality of life for those subjected to them. If you receive high levels of complaints, you will probably be subject to investigation by the regulator. Sometimes, this results in legal and monetary ramifications. Not only that, but it will also impact on your company’s reputation. Hedonic tone scores allow you to proactively engage with the community whilst implementing odour mitigation strategies.

Planning and Permitting Compliance

Silsoe Odours advise on remedial action, to help you limit the impact of unpleasant odours. We also provide qualitative data. You can use this to develop effective odour management plans. The data will also help satisfy the regulator and inform both planning and operational permit applications. Finally, hedonic tone is useful to determine the ‘safe zone’ required between new housing developments and local industry.


There are a number of odour assessments and testing services available. Depending on your individual odour challenge, you may require one, or a combination.

The laboratory at Silsoe Odours is UKAS accredited. We designed our testing services to help you understand the nature of your odour emissions. As well as hedonic tone, we offer odour intensity testing, odour characterisation, chemical analysis and odour detection threshold analysis.

You may also require one of our on-site odour services. These include odour sampling surveys, dispersion modelling, sniff surveys, smoke surveys and odour assessment surveys. We are also UKAS accredited for odour sampling.


Would you like to understand more about hedonic tone, or any of our odour assessments? Please get in touch. We have very experienced odour specialists who are happy to talk through your challenges. Give us a call on 01525 351396 or contact us here.

Odour Study Day

The Odour Study Day is a CPD certified one-day course which gives a comprehensive overview of odour management

What’s more, you can attend the Odour Study Day training course. You can learn more about all aspects of odour management. It is CPD certified, accredited by CIWEM and endorsed by the IAQM. Book early to guarantee a spot, as places fill up fast.

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