Odour Assessments for Planning Permission

The sense of smell plays a crucial role in our daily lives, influencing our emotions, memories, and overall well-being. Odour, in its various forms, can either be pleasant or unpleasant, let’s suppose you walked past a fish and chip store or restaurant and found yourself captivated by the mouthwatering aromas emanating from within. While pleasant, these scents can sometimes be inconvenient for those living nearby. But have you ever wondered what exactly defines Odour? I will try to delve into the concept of Odour, its units of measurement, the different types of Odours, and the best time to measure and analyse them.

What is Odour?

Odour, commonly referred to as smell or fragrance, is the perception of certain molecules in the air that stimulate the olfactory system. Our olfactory receptors, located in the nose, detect these molecules and send signals to the brain, resulting in the recognition and interpretation of specific scents. Odour is a complex sensory experience that can evoke various emotions, trigger memories, and even impact our behaviour.

Units of Odour Measurement:

To quantify and measure Odour, specific units and methods have been developed. One commonly used unit is the “Odour unit” (OU), which represents the concentration of a particular Odorant in the air. This unit is typically measured using instruments such as olfactometers, which assess the intensity of Odour perception.

Types of Odour:

Odours can be classified into different categories based on their origin and characteristics. Here are some common types of Odours:

1. Aromatic Odour: Aromatic Odours are typically pleasant and often associated with natural substances like flowers, fruits, and spices. These Odours are frequently used in perfumes and aromatherapy due to their positive effects on mood and well-being

2. Putrid Odour: Putrid Odours are highly unpleasant and often associated with decaying organic matter, sewage, or rotten food. These Odours serve as a warning sign of potential health hazards and are generally avoided.

3. Chemical Odour: Chemical Odours arise from various man-made substances and may have distinct characteristics. Some chemical Odours are harmless, while others may indicate the presence of toxic or hazardous materials.

4. Metallic Odour: Metallic Odours are often described as a metallic, tangy scent and can be associated with blood, certain minerals, or metallic substances. These Odours can sometimes be indicative of a medical condition or environmental factor.

    When is the Best Time to Measure Odour?

    The perception and measurement of Odour can vary depending on several factors, including time of day and environmental conditions. To obtain accurate measurements for an Odour Assessment, it is generally recommended to measure Odours during stable weather conditions when wind speed, wind direction, temperature etc. Early morning or late evening hours are often considered ideal due to reduced activities and traffic that can influence the dispersion of Odours.

    Why Might You Need an Odour Assessment for Planning Permission?

    Odour Assessments are often required for planning permission applications, particularly in industries that may produce substantial odour emissions, such as restaurants, livestock farms, and chemical facilities etc. The primary purpose is to evaluate the potential impact on the surrounding environment and nearby communities. By conducting an Odour Assessment, applicants can demonstrate their commitment to environmental sustainability and ensure compliance with local regulations. This assessment helps identify mitigation measures to minimize or eliminate odour nuisance to protect the quality of life for residents.


    Understanding the nature of Odour, its units of measurement, and the different types of Odours can enhance our awareness and appreciation of the olfactory experience. Whether it’s enjoying the pleasant fragrance of flowers or identifying potential hazards through unpleasant Odours, our sense of smell plays a significant role in our daily lives. By recognizing the best time to measure and analyse Odours, we can gather valuable information that contributes to improving air quality, health, and overall well-being.

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