What is Olfactometry? | Measuring Odour Concentration Under BS EN 13725
Olfactometry is the process of measuring the concentration and intensity of odour in air samples. It is the core analytical technique behind standardised odour measurement and is defined within BS EN 13725:2022.
The technique is widely used to assess odour emissions from industrial, agricultural and waste management sites. It is useful when robust, defensible data is needed for environmental management, regulatory compliance and planning applications.
Regulatory agencies and industries may use it to:
- Assess an operator’s impact on the surrounding community
- Evaluate odour nuisance complaints
- Determine whether odour control measures are effective
- Identify and mitigate sources of odour emissions
What is Dynamic Olfactometry?
Dynamic olfactometry is the specific method used to measure odour concentration under controlled laboratory conditions. It works by diluting an odour sample with clean air and presenting it to a trained human panel for assessment. As a result, the odour concentration in the sample can be calculated in European odour units (ouE/m³).
This method is standardised under BS EN 13725:2022, which ensures results are repeatable across UKAS-accredited odour laboratories.
Olfactometry uses human assessors because the nose remains the most sensitive instrument for odour detection. Odour panels must be carefully selected, screened and trained to achieve reliable odour data. Explore the wider process of odour testing in our dedicated guide.
How Olfactometry Works
The process follows a tightly controlled sequence designed to ensure reliability, repeatability and objectivity.
| Action | Detail | |
|---|---|---|
| 1 | Odour Sample Collection | Specialists collect odour samples from identifiable sources and transport them to the laboratory for analysis. |
| 2 | Dilution | The laboratory operator dilutes the sample with clean air to a specific concentration that is faint, but just detectable. |
| 3 | Odour Panel Assessment | The odour panel assesses the sample using the olfactometer. |
| 4 | Calculation | The results produce a final odour concentration (ouE/m³) and intensity value for each sample. |
| 5 | Results | Clear, robust and defensible results for environmental management, compliance and decision making. |
Learn more about odour sampling surveys and the different types of analytical odour testing services involved with olfactometry.
Why Olfactometry is Important
Olfactometry provides a consistent, repeatable and defensible way to quantify odour emissions.
It is used across sectors, including wastewater treatment, agriculture, waste management, industrial processes and planning.
Operators can use olfactometry to support:
- Environmental permitting
- Planning applications
- Odour impact assessments
- Regulatory compliance reporting
- Evaluation of odour control systems
For the regulatory framework behind olfactometry, see EN 13725:2022 – The European Standard for Odour Measurement.
The Role of the Olfactometer
The olfactometer is a scientific instrument designed to precisely control the dilution and presentation of odour samples.
Using the olfactometer allows odour labs to:
- Measure odour concentration accurately and repeatably
- Comply with BS EN 13725:2022
- Control dilution of potentially strong odour samples
By standardising sample delivery, the olfactometer ensures that results are objective and scientifically defensible. This is important for regulatory and planning purposes.
Safety & Risk Management in Olfactometry
Some odour samples may contain compounds that pose health risks at elevated concentrations. One example is hydrogen sulphide (H₂S), a gas commonly associated with sewage, waste and industrial odours.
At low concentrations, H₂S can irritate the eyes, nose and throat, or cause headaches and nausea. At significantly higher concentrations, it can become dangerous. For this reason, olfactometry laboratories must carefully control exposure throughout sampling and analysis.
Under BS EN 13725:2022, dynamic olfactometry must use strict laboratory procedures to ensure exposure levels remain well within safe limits.
| Protection Measures | Purpose |
|---|---|
| Personal Protective Equipment (PPE) | PPE, including gloves, eye protectors and personal gas sensors, protects sampling teams from exposure to chemicals and other hazardous materials when on site. |
| Hydrogen Sulphide (H₂S) Screening | Samples are checked for H₂S before presentation to the odour panel. This ensures they are not exposed to dangerous levels. |
| Laboratory Ventilation | Maintains clean, temperature-controlled air and prevents the build-up of harmful fumes or gases. |
| Controlled Laboratory & Site Procedures | Staff follow correct procedures for handling and testing odour samples, ensuring consistent and safe conditions. |
| Daily Routines | Odour panel members follow careful health, safety and hygiene procedures to minimise risk. |
At Silsoe Odours, these controls form part of our wider UKAS-accredited odour testing laboratory procedures and quality systems.
Speak to an Odour Specialist
In summary, dynamic olfactometry remains the gold standard method for measuring odour concentration. When carried out in accordance with BS EN 13725:2022 within a UKAS-accredited laboratory, it provides robust, defensible data for operators, regulators and consultants.
As a leading UK odour specialist, Silsoe Odours supports operators with precise, reliable odour measurement and expert interpretation.
If you would like advice on odour measurement or laboratory testing, our team can help.
Call: 01525 860222
Follow us: LinkedIn | X (Twitter) | Facebook
References:
World Health Organisation – Air Quality Guidelines for Europe
Health & Safety Executive – Workplace Exposure Limits
United States Department of Labor; Occupational Safety and Health Administration – Health Hazards
Frequently Asked Questions
What is an Odour Unit (ouE/m³)?
An odour unit (ouE/m³) is the standard measurement used to express odour concentration in air. It represents the number of dilutions required for an odour to become just detectable to a trained odour panel.
Why are Human Panellists Used in Olfactometry?
The human nose remains the most sensitive and reliable instrument for detecting many environmental odours. Dynamic olfactometry measures how odours are perceived by people, so trained human assessors are essential to the process. Under BS EN 13725:2022, odour panel members must be carefully selected, screened, and monitored to ensure they provide consistent, repeatable responses.
Is Olfactometry Needed for Planning Applications?
Planning authorities may request olfactometry data as part of an odour impact assessment if a proposed development could generate odour emissions or expose sensitive receptors to existing odours.
This commonly applies to sectors such as waste management, wastewater treatment, agriculture, food production and industrial processing.
Published March 2023. Most recently updated May 2026.
