How to Conduct an Effective Odour Impact Assessment
Understand Odour Emissions & Stay Compliant with Silsoe Odours
Operators are often unsure what an odour impact assessment actually involves. In practice, it is a structured process for measuring, characterising and interpreting odour emissions from a site.
"In this article, I explain the process behind our most popular service, the Odour Sampling Survey. I also provide an overview of some other types of odour impact assessment. So, continue reading to understand what to expect when working with our specialist team." James Sneath, Technical Manager, Silsoe Odours.
This work sits within the wider odour measurement and analysis process. Different techniques can also be combined for a more detailed understanding of odour emissions. You can learn more in our guide to measuring odour.
Why Conduct an Odour Impact Assessment?
An odour impact assessment is a structured approach, used to:
- Measure odour emissions from specific sources
- Assess how odours behave in the environment
- Interpret the potential impact of odours at surrounding receptors
The following table shows how data from these assessments can be used:
| Purpose of Assessment | Related Guide |
|---|---|
| Validate odour complaints | ↗ Odour Complaints & How to Handle Them |
| Support environmental compliance requirements | ↗ Odour Management & Compliance |
| Support planning applications | ↗ Odour in Planning & Development |
| Evaluate operational odour control efficiency | ↗ Controlling Odour Emissions for Compliance |
The Odour Impact Assessment Process
Although every project is tailored to site conditions, most assessments follow four key stages.
1. Briefing – Define Your Assessment Needs
To start, we will ask for as much information as you can provide about your odour issue. Sometimes, you will have a clear understanding of your needs and timeline. In other cases, you might be unsure. We will work with you to find the best solution for your requirements.
Key actions:
- Outline your operational processes and potential odour sources
- Indicate any timelines or permit deadlines
- Decide if an odour sampling survey, sniff survey or dispersion model is most suitable
- Agree on project scope, timelines, and budget
At this stage, we determine whether the assessment will involve odour sampling surveys, sniff surveys or dispersion modelling. To understand which odour service you need, read our guide on odour assessment methods.
2. Planning – Prepare for Accurate Assessment
After you approve your survey details, we get on with planning. Good planning ensures safe and effective sampling. Our planning process includes:
Site Review
Identify access points, health & safety requirements and hazards
Odour Sources
Identify all key odour emission points
Weather & Topography
Changes in wind direction can affect sampling results
Client Approval
Confirm the methodology and survey plan before beginning
All our odour sampling and testing is UKAS-accredited.
3. Sampling – Collect Reliable Odour Data
On the day of the odour sampling survey, we:
- Arrive on-site and adapt to conditions (e.g., locked gates, weather changes)
- Collect odour samples from the sources we identified during planning
- Use specialist equipment to take all samples in triplicate, ensuring reliability and accuracy
- Record field observations and operational conditions
Silsoe Odours were recommended to me by colleagues, as they are always very good and knowledgeable. I engaged them for emissions monitoring of an oil/fuel depot and had a good experience. Their odour consultants arrived at site as arranged and completed the work efficiently and effectively.
Liam Shelmerdine, Redmore Environmental
In some cases, we may use a sniff survey or odour dispersion modelling instead. We will select the method based on the objective. For example, measuring emissions or predicting off-site odour impact.
Sniff surveys involve trained assessors recording odour in the field. They note whether odour is present, how strong it is, and what it smells like.
This helps show how people may perceive odours outside the site boundary.
They are often used to validate complaints, support planning applications, or check site conditions.
Odour dispersion modelling uses site data and weather information to predict how odours may travel away from a site.
It produces maps showing where odours are likely to be detected.
Modelling is commonly used for design and planning, and for forecasting potential odour impacts.
4. Laboratory Testing – Quantify Your Odour Impact
After collection, we transport all odour samples to our UKAS-accredited laboratory for odour testing and analysis.
Depending on your needs, we can test odour samples for:
- Odour concentration
- Odour intensity
- Odour characterisation
- Detection thresholds
- Chemical analysis
- Hedonic tone
We can also test samples collected by operators and consultants, provided the methodology complies with BS EN 13725:2022.
5. Reporting – Clear Findings & Recommendations
Finally, we present all findings and recommendations in a comprehensive report. Our reports are concise, easy to navigate and scientifically accurate. You can use them to support your efforts to control odour emissions and maintain compliance with permits.
An Odour Impact Assessment from Start to Finish
See how an odour sampling survey is carried out in practice:
Need Support with an Odour Impact Assessment?
I have outlined the stages for one of our odour evaluation methods. If you would like to learn more, please get in touch. For odour assessments, sampling or testing, our team of expert odour consultants can guide you.
Call: 01525 860222
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FAQs
Do I Need an Odour Impact Assessment for My Permit?
Yes. Many operators benefit from proactive assessment to demonstrate compliance and minimise complaints.
What’s the Best Method for Odour Assessment?
It depends on your site and emissions. Options include sampling surveys, sniff surveys, and dispersion models. Sometimes, you will need a combination of different assessments.
Originally published March 2021. Last updated April 2026.
