Building 42 Wrest Park Silsoe BEDFORD Bedfordshire MK45 4HP
01525 860222

Sniff Surveys


A sniff survey is an independent subjective survey, which measures the impact of odours. It identifies the specific odour source, or sources, where it’s not known.

Silsoe Odours uses the results of the sniff survey to provide our customers with scientific evidence relating to your odour emissions. Our report will enable you to measure, evaluate and ultimately control the odours which may be produced by your plants and processes.

Our sniff surveys use a panel of qualified odour assessors, in line with BSEN16842-2 guidelines, to determine the effects of odour dispersal over a determined period, in a range of meteorological conditions.


We provide the results of the sniff survey to our customers in an easy-to-read report, which contains details that are helpful for informing odour management plans and implementing odour control measures. Many of our customers find this extremely useful for satisfying the requirements of the regulator, particularly following public complaints relating to malodours.

A field odour impact survey is useful for:

– An odour impact assessment without requiring access to site
– Identifying odour sources where multiple sites are in close proximity
– Confirming the results of dispersion modelling
– Informing odour management plans
– Confirming the details of odour complaints


Sniff surveys use a series of observation points located downwind of the suspected source of the odour, detailed records are kept in order to track its intensity and frequency. The term ‘plume’ describes the trajectory of the odour and the dispersal pattern created as it meets atmospheric turbulence. Data is recorded at regular intervals, noting meteorological divergences. The human assessors use the ‘sniff test’ to determine the absence or presence of the odour and its journey is plotted by noting where the smell is at its most intense, and at what point it disappears.

The composition of the panel for any given sniff survey will remain constant throughout the testing process and the number of assessors will be determined by the manner of assessment:

Plume Method – a minimum of five assessors.
Dynamic Plume Method – a minimum of two assessors.

assessor wind flow chart


The simplified diagram in Fig. 1 illustrates the idealised progression of the assessors. The wind indicated by the arrow 1, the odour source is at 2. Black spots indicate where an odour is detected and circles where no odour is detected. The plume extent is drawn between odour present and no odour points. Panel members will make an assessment every 10 seconds.


Our sniff surveys are conducted by our panel of qualified odour assessors, and led by one of our highly experienced odour experts. All our odour assessors are selected and continually checked according to the requirements of BSEN13725:2022.

The odour panel will use a series of observation points, located downwind of the suspected odour source, to track its intensity and frequency. These observations are conducted in line with Institute of Air Qualty Management (IAQM) Guidance and/or European Standard BSEN16842-2.

Our sniff surveys are designed to respond to subjective experiences of odour impact, representative of the kind of complaints our customers may face from members of the public.

Client testimonials

Don’t take our word for it – here’s what our clients say:

We were seeking planning permission for a development which is adjacent to a site with known odour issues. We had completed our own survey, but the council asked for an independent odour assessment. We approached Silsoe Odours as had previously had a good experience with them for olfactometry work, and knew they had prior knowledge of the site. I was particularly impressed with the way they presented and summarised their data. It was easy to understand and presented in such a way that the layman could understand. I wouldn’t hesitate to recommend Silsoe Odours and look forward to working with them again in the future.

Graham Harker

Peter Brett Associates

To find out more about sniff surveys, call our team on 01525 860222.