Wave Dynamics GuidesOdour Assessments Explained
How odour is assessed for planning and licensing: sniff surveys, the FIDOL factors, odour modelling and kitchen extract odour risk assessments.
In Short
An odour assessment looks at whether smells from a development, such as wastewater treatment, waste handling, agriculture, food production or a commercial kitchen, are likely to cause annoyance at nearby homes and businesses. It can use site surveys, odour dispersion modelling or a risk-based assessment depending on the source.
- Odour impact depends on frequency, intensity, duration, offensiveness and location (FIDOL).
- Surveys use trained assessors; modelling predicts odour concentrations over a year.
- Commercial kitchens use a risk assessment to size extract and odour control.
- Mitigation can include abatement equipment, enclosure and higher discharge points.
When Is an Odour Assessment Needed?
Planning authorities and the EPA ask for odour assessments for uses with a known odour risk: wastewater and sludge treatment, composting and anaerobic digestion, intensive agriculture, rendering and food processing. Restaurants and takeaways with commercial kitchens near homes usually need a kitchen odour risk assessment.
Odour Surveys
Sniff surveys use trained assessors walking set routes around a site to record odour intensity, character and extent. They are useful for existing sites, complaint investigations and establishing a baseline before a new development.
Odour Modelling
For larger or new sources, emission rates measured or taken from published data are used in a dispersion model to predict odour concentrations, usually as the 98th percentile of hourly values over a year. These are compared with benchmarks that reflect how offensive the odour is.
Kitchen Extract Odour Risk
For commercial kitchens, the type of cooking, the size of the kitchen and the distance to receptors decide the level of odour control needed, from grease filtration to carbon filters, UV-ozone or electrostatic precipitators, and the height and position of the discharge point.
Frequently Asked Questions
What does FIDOL stand for?
Frequency, Intensity, Duration, Offensiveness and Location. These factors together decide whether an odour is likely to cause annoyance.
Do takeaways need an odour assessment?
Many planning authorities ask for one where a hot food use is proposed close to homes, particularly with an extract system discharging near windows.
This guide gives general information and is not a substitute for project-specific advice. Requirements change, so always check the current regulations, guidance and your planning conditions. Ask our team about your project.
Jon Maguire (BSc Hons MIOA) brings over 8 years of expertise in acoustic consultancy, specialising in environmental acoustics with a focus on 3D modelling, assessments, and detailed design for industrial, commercial, and energy projects. He has lead noise assessments for key clients while thriving in multidisciplinary environments. Jon’s diplomatic communication skills are ideal for stakeholder consultation.
Jack is a Field Engineer at Wave Dynamics, supporting the delivery of environmental monitoring and acoustic consultancy services through detailed on-site fieldwork. He has hands-on experience in noise monitoring, vibration monitoring, and dust monitoring across a variety of infrastructure, construction, and environmental projects. Jack is involved in the setup, operation, and maintenance of monitoring equipment, ensuring accurate data collection in line with relevant standards and project requirements. He works closely with consultants and project teams, providing reliable field support that underpins high-quality assessments and reporting.
Aidan is the Director for all U.K Operations and has worked in multiple industries including for clients in the UK and internationally operating in the residential, industry, healthcare, education, and construction sectors.
