Odour Measurement: How to Measure Odour
It is essential to select appropriate odour measurement methods and equipment to achieve accurate, defensible results.
At Silsoe Odours, our UKAS-accredited laboratory measures and analyses odorous emissions in accordance with the European odour standard BS EN 13725:2022 and ISO 17025. We provide objective data to help operators understand, assess and manage odour emissions from their sites.
But how exactly do we measure odour?
In this guide, you will learn:
- What odour measurement is
- How odour samples are collected
- The equipment used for accurate odour measurement
- The difference between odour sampling surveys and sniff surveys
What Is Odour Measurement?
Odour measurement is the process of quantifying odour properties in an air sample. It includes several key metrics used to describe and quantify odours in a consistent and scientific way:
| Odour Metric | Definition |
|---|---|
| Odour Concentration | The amount of odour in the air, expressed in odour units per cubic metre (ouE/m³). |
| Odour Intensity | How strong the odour is perceived to be. |
| Hedonic Tone | Whether the odour is perceived as pleasant, neutral or unpleasant. |
| Odour Character | The qualitative description of the odour (e.g. ammonia-like, floral, chemical) |
| Odour Detection Threshold | The minimum concentration at which an odour is detectable. |
In the UK and Europe, odour concentration is measured in odour units per cubic metre (ouE/m³) using a method called dynamic olfactometry, as defined in BS EN 13725:2022. The process often involves trained human assessors.
You may also see the term odorimetry, although this is used less commonly in UK practice.
Assessing odours enables operators to understand their strength, quality and potential impact on nearby communities. This can be useful for environmental compliance, planning, abatement testing, and process optimisation.
How to Measure Odour
Generally speaking, there are two primary methods of odour measurement:
Odour Sampling Surveys
Conducted from: Known site sources
Output: Quantitative data
We collect samples from a site and analyse them in our UKAS-accredited odour laboratory, using dynamic olfactometry.
This method provides quantitative odour concentration data, as well as assessments of intensity, hedonic tone and character.
Laboratory testing is commonly used for:
- Environmental permit compliance
- Planning applications
- Abatement testing
- Process optimisation
Field Odour Surveys (“Sniff Surveys”)
Conducted from: Field
Output: Qualitative data
Specialist odour panellists assess odours directly on-site.
Sniff surveys help to map odour impacts in surrounding areas.
This can be particularly useful for investigating odour complaints, providing evidence-based insights into potential odour sources and impacts.
Sniff surveys are also widely used in planning applications, where understanding off-site odour impacts is required.
These methods are often used alongside odour testing for detailed laboratory analysis.
Odour Measurement Equipment: Sampling
Have you ever heard the mantra “proper preparation prevents poor performance”? Here at Silsoe Odours, we are entirely on board with the ‘5Ps’. That is why we begin every odour measurement project by thoroughly researching the site.
We consider:
- Meteorological conditions
- Site layout
- Potential odour sources (for odour sampling surveys)
- Safety considerations
Crucially, our team has extensive expertise and holds UKAS accreditation for odour sampling and testing.
It is also essential that we use the right odour measurement equipment. We carefully select the right tools for each job.
Here is a quick run-down of some of the equipment we use:
Nalophan Odour Sampling Bags
On site, we collect odour samples using Nalophan odour sampling bags. We manufacture and test the bags at our laboratory according to the requirements of European odour standard EN 13725:2022. We are accredited to do this under ISO 17025.
Rigid Lung Barrels
We attach the Nalophan odour sample bag to direct point sources where there is positive pressure. Otherwise, we use a rigid lung barrel to evacuate the air, then draw the odour sample into the bag using a vacuum pump.
Lindvall Hood
A Lindvall hood is a piece of equipment that allows us to measure odour from open sources. We place the hood over a source and allow it to fill. We can then draw off the odour from the hood using a Nalophan sample bag and rigid lung barrel.
Dilution Probe
Sometimes we need to dilute a sample at the source to stop condensation from forming. In this case, we will use a dilution probe. By preventing condensation, we can ensure more effective odour measurement.
Odour Measurement Equipment: Laboratory Testing
Once we have collected odour samples, we return them to our laboratory for testing and analysis. To do this, we use a process of dynamic olfactometry.
The Human Nose
The human nose is the most effective sensor of odour and, therefore, our most important tool for measuring odour.
We use a panel of carefully selected, screened and trained assessors (‘odour panel members’) to conduct our olfactometry testing.
Specialist odour panellists also conduct sniff surveys.
Olfactometer
The olfactometer is a device that dilutes an odour sample to a known concentration. It then presents the sample to our specialist odour panel. They take part in a ‘forced choice’ progression of odour assessment until they have established the sample’s odour concentration.
This produces quantitative, reliable data in accordance with BS EN 13725:2022.
In addition to odour concentration, we can also test samples for chemical analysis, odour detection threshold, odour intensity and odour characterisation.
What’s Next?
Understanding how to measure odour is just the first step. Once you have accurate data, the next stage is knowing how to apply it effectively. Depending on your needs, you may want to explore:
| Guide | What’s Covered |
|---|---|
| ↗ Odour Impact in Planning & Development | How odour measurement supports planning applications and environmental compliance. |
| ↗ Odour Complaints & How to Handle Them | How to investigate and respond to odour complaints using sampling surveys and analysis. |
| ↗ A Seasonal Guide to Managing Odour | Practical strategies to reduce on-site odour emissions using monitoring and measurement data. |
Each of these guides links the technical measurement insights you’ve learned here to real-world applications, helping you manage odour confidently and compliantly.
Find Out More About Odour Measurement
So you should now have a good idea of what goes into measuring odour, from preparation to collection to analysis. However, if you have any queries, we would be more than happy to help. Our team has many years of expertise and experience and can help with your odour challenge.
To reach the Silsoe Odours team:
Call: 01525 860222 | Email: info@silsoeodours.co.uk
Follow us on social media: LinkedIn | X (Twitter) | Facebook
Frequently Asked Questions
Why Is Odour Measurement Important?
Odour measurement is crucial because it provides objective, quantifiable data on the properties of odours emitted from a site. By measuring odours, operators can:
- Ensure compliance with environmental permits and regulations
- Support planning applications by demonstrating control of odour impacts
- Investigate complaints effectively with evidence-based results
- Evaluate and optimise odour abatement systems
- Understand community impact, helping to maintain good neighbour relations
Without measurement, decisions rely on perception rather than evidence.
What is Odorimetry?
Odorimetry is another term for odour measurement, used internationally. It refers to the assessment of odour concentration, intensity, hedonic tone, character, and detection threshold using trained human assessors.
How is Odour Measured?
Generally, odour is measured in one of two ways. Firstly, by collecting air samples from a site and then analysing them in a laboratory using dynamic olfactometry. Secondly, by conducting on-site field surveys (‘sniff surveys’).
What Odour Measurement Equipment Is Used?
Equipment includes olfactometers, Nalophan sampling bags, rigid lung barrels, Lindvall hoods and dilution probes.
Published: July 2021. Last updated: April 2026.
