What is odour?
Odour is a distinctive smell, most often an unpleasant one. It is perceived by our brains in response to chemicals and gases present in the air we breathe. It results from a two stage process;
- First the brain senses the chemical/ gas stimulus
- It then interprets it based on previous life experiences. Natural variation in sensitivity and life experiences can result in individuals having different responses to the same odour.
Because the response to odour is processed in our brains, other senses such as sight and taste, and even our upbringing, can influence our perception of odour and whether we find it acceptable, or offensive. For example, to those working in a particular ‘industry,’ odours that are widely perceived as offensive may be acceptable to them due to their familiarity.
Humans have a sensitive sense of smell and can detect odour even when chemicals and gases are present in very low concentrations. Because odour is a human perception, it is extremely difficult to measure as is possible for other ‘nuisance impacts’ like noise and light. There is general agreement in the scientific community that frequency, intensity, duration, offensiveness and location (FIDOL) are factors that should be considered when assessing odour nuisance.
Odour character, perception and effects . . .
Odour character is what a substance, chemical or gas smells like. Due to variance in people’s perception of an odour, the same thing may be described very differently by different people. Odours can affect people and the environment in a number of ways;
Odour sensitivity: Everybody has a different sense of smell. The normal population ranges from those who are insensitive to odour, all the way through to people who are hyper-sensitive to odour.
Hedonic tone: Hedonic tone is how an odour is rated on a ‘pleasantness’ scale – from extremely unpleasant to extremely pleasant.
Intensity: This is the strength of an odour
Perception: The perception of an odour can change depending on the concentration, intensity, time, and frequency, alongside life experiences impacting emotional responses to the same odour, and medical conditions which can suppress or enhance odour perception.
Effects: Odour has a wide range of impacts on individuals ranging from headaches, breathing issues, and other physical symptoms through to emotional impacts such as annoyance, stress, and depression – all result in a reduced quality of life and explain why odour management and control is vital.
Why odour management and control are important . . .
Community consultation:
Because odour is an effect of an individual’s perception, one of the most important actions to support its’ successful management, is to build a positive relationship with the community experiencing the effects, through regular liaison. Community liaison groups usually include management and environmental staff from the discharging company (discharger), representatives of the local community, and regional council members.
Open, honest and transparent communication is valuable to enable a responsive relationship. This helps identify and prioritise concerns, and required mitigation between a community and the discharger before escalation or formal complaints – it enables co-operation to find solutions to adverse odour effects.
Odour Control
Odour sources that require treatment need to be captured and ducted to control equipment. Some gas streams require pre-treatment steps, including removal of particulate, and cooling or condensation to remove moisture and reduce temperature, depending on the final control option. Odour control equipment is generally limited to a small range of technologies that have been used for many years. Most technologies are well understood and have proven performance. Our next article will look at how Taranaki Bio Extracts manages odour treatment and control on their site.
Ends.