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 EN 13725 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 the properties of odour in an air sample. It encompasses key measurements, including:

• 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 EN 13725. The process often involves trained human assessors. You may also see the term odorimetry, which is sometimes used internationally to describe odour measurement.

Assessing odours enables operators to understand their strength, quality, and potential impact on nearby communities. This can be useful for things like environmental compliance, planning, abatement testing, and process optimisation.

How to Measure Odour

Generally speaking, there are two primary methods of odour measurement:

• 1. Odour Sampling Surveys
  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

• 2. Field Odour Surveys (“Sniff Surveys”)
  Specialist odour panellists assess odours directly on-site. Sniff surveys help to map odour impacts in surrounding areas. This can be helpful for investigating complaints and in planning applications.

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 piece of equipment for odour measurement.

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 data that is quantitative, reliable and 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:

• Odour Impact in Planning & Development – Learn how odour measurement supports planning applications and environmental compliance

• Odour Complaints & How to Handle Them– Find out how to respond to odour complaints using sampling surveys and analysis.

• A Seasonal Guide to Managing Odour – Explore strategies to reduce on-site odour emissions, incorporating and informed by measurement results.

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 accurate odour measurement, decisions on odour management are based solely on perception, which can be subjective and inconsistent. Proper measurement provides a reliable foundation for action, reporting, and regulatory compliance.

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.

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