As the warmer months approach, many of us naturally look forward to spending more time outdoors, relaxing in our gardens, enjoying communal green spaces, or simply opening our windows to let in the breeze.
With this seasonal shift comes the expectation of a breath of fresh air, both figuratively and literally. Yet that expectation is not always guaranteed. The quality of the air we enjoy outdoors depends heavily on the absence, or presence, of nearby odour producing sources. However, the very conditions that make summer so pleasant for us also create the perfect environment for odours to worsen.
During the warmer months, the atmosphere often becomes more stable, with lower wind speeds and less vertical mixing of air, preventing odours from dispersing and diluting. These meteorological conditions, common between April and September, form the “worstcase” conditions for odour exposure, making this period the most important window for accurate odour observations.
For anyone involved in new developments, developers must consider whether nearby odour emitting activities, such as waste facilities, industrial operations, food manufacturing, or agricultural processes, could affect the future amenity of occupiers and site users. Local planning authorities are increasingly aware of the significance of odour as an environmental constraint. As a result, they now routinely require an odour assessment as part of planning submissions where there is a realistic risk of odour impact.
There are various methods of odour assessment available, ranging from predictive modelling to observational field surveys. The use of the human nose to measure odour (a technique called sniff testing) is an unmatched observational technique due to the nose’ sensitivity, speed and range of application. Although sniff testing involves a subjective human response, when carried out systematically by odour assessors within a normal range of odour sensitivity, it becomes a powerful and trusted tool.
Given its reliance on human perception, odour assessors must demonstrate that their sensitivity falls within an accepted standard range as some people might be over or under sensitive to odour as can be seen inthe figure below:
To provide a realistic and defensible assessment of odour assessment using sniff tests, assessments must be based on worst case seasonal data. By gathering data between April and September, when odour emissions are most pronounced and meteorological conditions are least favourable for dispersion, developers can ensure that their assessments reflect the actual experience of future site users.
Our Air Quality team recently completed formal odour acuity testing in accordance with the BS EN olfactometry standard, all passing, with each falling within the normal sensitivity range (20–80 ppb for Nbutanol). This accreditation strengthens the reliability of our field assessments, provides confidence in our findings, and ultimately supports more robust planning outcomes.
As we enter the months where worse case odour impacts are likely, it becomes increasingly important for developers, planners, and communities to understand the role that odour can play in shaping local amenity. Thorough, evidence-based odour assessments are not just a regulatory requirement, they are an essential component of creating places where people genuinely want to live and spend time.
If you would like to explore how a bespoke odour assessment could support your development or address site specific concerns, please contact our air quality team who would be happy to help.