What Is Olfactometry?

Simply put, olfactometry is the process of measuring the concentration and intensity of odour.

As odour consultants, we receive many requests for this service. Generally, we refer to it as odour testing, and it’s the bread and butter of what we do here at Silsoe Odours. Olfactometry is often used for environmental monitoring of industrial or agricultural operators, where controlling odorous emissions is important for environmental and health reasons. 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

Olfactometry uses human assessors, because the nose remains the most sensitive and accurate odour-detection instrument.

How Does Olfactometry Work?

At Silsoe Odours, we use carefully selected, screened and trained odour panel members to conduct testing in our UKAS-accredited odour laboratory.

Our laboratory operator dilutes samples of air containing odour with clean air to achieve specific concentrations. They then present these samples to the odour panel.

Using a process of forced choice, panel members detect and rate the intensity and character of the odour. From their responses, we can calculate the concentration of the odour in the sample, in ouE/m³.

We can also use olfactometry alongside chemical analysis to assess a sample’s odour profile.

The Olfactometry Process

The process typically involves the following steps:

• Odour Sampling Survey
  Our odour consultants will collect odour samples from identifiable sources on site. When they have done this, they transport the samples back to our UKAS-accredited odour laboratory for olfactometry analysis.

• Dilution
  Our Laboratory Operator dilutes the sample with clean air, to a specific concentration level that is incredibly faint, but just detectable.

• Presentation to the Panel
  The Laboratory Operator presents the odour sample to our trained odour panel members using the olfactometer. They do this in our specialist odour laboratory. It is a highly controlled environment, with carefully designed air conditioning and temperature specifications.

• Evaluation
  Odour panel members rate the intensity and character of the odour.

• Calculation
  The results are used to produce a final odour intensity value for each sample. Additional parameters can also be assessed. These include concentration, intensity, character, chemical analysis, odour detection threshold and hedonic tone (pleasantness).

Why Do You Need An Olfactometer?

The olfactometer is a scientific instrument designed to precisely control the dilution and presentation of odour samples.

Using the olfactometer allows us to:

• Measure odour concentration accurately and repeatably
• Comply with BS EN 13725:2022
• Maintain strict safety controls for odour panel members

Without an olfactometer, odour measurement would lack the standardisation and defensibility required for regulatory or planning purposes.

While olfactometers are critical to environmental odour assessment, they are also used in psychology, neuroscience, medical research and product development.

How Can Odour Impact Human Health?

A volatile organic compound (VOC) is an organic chemical that evaporates easily at room temperature, allowing it to enter the air as a gas. VOCs are produced both naturally and through human activity. Many have a strong odour that can be detected at low levels.

VOCs also contribute to air pollution and can cause health issues. For example, one such VOC is hydrogen sulphide (H₂S) – a common component of the samples we collect and analyse. H₂S is a colourless, flammable gas with a characteristic rotten egg odour.

At low concentrations, exposure may cause eye, nose and throat irritation, headaches, nausea and dizziness. In very extreme circumstances, it can pose serious health risks or even death.

Importantly, exposure levels are carefully managed during olfactometry testing to remain well within safe limits.

This chart explains the possible health effects associated with different exposure levels.

How We Protect Our Odour Panel

Our odour consultants and panel members can potentially be exposed to odorants. With this in mind, we have strict precautions to ensure our staff’s safety. These include:

Personal Protective Equipment (PPE)

Our consultants must wear appropriate PPE when they collect odour samples. For example, gloves, eye protectors and personal gas sensors to detect hydrogen sulphide and ammonia. In this manner, they can protect themselves from exposure to chemicals and other hazardous materials.

Hydrogen Sulphide Testing

We are careful to take precautions to make sure the team aren’t exposed to dangerous levels of hydrogen sulphide (H₂S), from the point where we collect samples right through to testing in the olfactometry lab. Primarily, we use a Jerome, which is a type of portable gas detector. We use it to check if the sample is safe to be analysed. On site, we check the H₂S levels where it is safe to do so, record the details and transfer to the lab. Then when we receive the sample in the lab, we re-test and record all the results again. If the Jerome records dangerous H₂S levels, we dilute the samples to a safe working value before presenting it to the odour panel.
Stephen Pollock – Laboratory Operator, Silsoe Odours

Adequate Ventilation

We have a highly controlled ventilation system in place in our odour lab. It serves two purposes. Firstly, to keep the air clean and temperature controlled. Secondly, to prevent the buildup of harmful fumes or gases that could expose the odour panel to high concentrations of odorants.

Proper Training

All of our odour panel members and laboratory operators receive appropriate training on safely handling samples and how to use the olfactometer.

Health Screening

Odour panel members should not have any pre-existing medical conditions that may put them at risk from exposure to odorants.

Sampling Procedures

Our staff handle odour samples with care to prevent leaks. They also conduct all sampling and testing procedures in a safe and controlled manner.

Emergency Procedures

We have clear emergency procedures in place in case of any accidents.

Personal Hygiene

Odour panel members must practice good personal hygiene. They must wash their hands regularly and avoid touching their eyes, mouth or nose during testing. This helps prevent the spread of contaminants and infections.

Regular Breaks

We give our odour panel regular breaks to rest and recover. Being fully alert helps prevent mistakes from occurring.

Speak to the Olfactometry Experts

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 one of the UK’s leading odour specialists, Silsoe Odours supports operators with precise, reliable odour measurement and expert interpretation.

If you would like to discuss your odour challenge, please contact us on 01525 860222. You can also email info@silsoeodours.co.uk or click the button below.

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