Column | Applying the art of perfumery to spatial design

The sense of smell is the first sense that people use after birth. Humans can detect up to a trillion different odours, yet anthropologists have found that in all known languages, there are fewer words that refer explicitly to our experience of smells than there are for any other sensation.

People’s perceptions, experiences and memories of a place are significantly shaped by the smells that they associate with and have detected in that place. However, despite its pervasiveness, persistence, and integral connection to emotional memory, the significance of the sense of smell is vastly underestimated in discussions of sensory urban design. Human olfactory senses have evolved to detect danger from unpleasant smells. Hence, even when urban smells are addressed, the focus is primarily on controlling nuisance odours, arising from sewage and air pollution.

The ‘smellscape’ of a place has widespread implications, ranging from public health to property valuation. Understanding how people sensually experience urban environments allows for the identification of processes for managing urban smell environments, and for the active incorporation of smell into spatial design.

Smellscape as an identity

The smellscape of a city could earlier be distinguished by its signature scents. However, smellscapes have changed dramatically over the last century as a result of globalization. Many towns have lost their uniqueness and have become clone towns.

A smellscape is a social intermediary and a key indicator of human activity, revealing cultural behaviours ranging from culinary customs to prevalent professions and popular pastimes. It can also reveal the presence of flora and fauna as well as the quality of local governance in terms of sanitation and waste management.

A smellscape acts as a spatial-emotional intermediary. Smells are invisible yet tangible elements whose individual and combined impacts with other sensory perceptions connect an individual's experience with the social structure of a place. They affect our moral judgment and how we categorize neighbourhoods in socio-economic hierarchies. This can set expectations for potential real estate and business investors, as well as tourists.

A city's smell should be tailored not only for instantaneous gratification but also for the creation of lasting memories and to enable people to experience a sense of place. Smells are remembered longer than visual images and, through recollection and association, can transport people back in time. This makes investing in smellscapes financially viable in terms of placemaking and destination branding. Petrichor, or the fresh, earthy fragrance of the first rain on dry soil, was promoted by the state of Kerala in southern India to draw tourists to its monsoon ambience. The magical scent of petrichor brought to life through compelling text, fit seamlessly within the visuals of a wet tropical haven and auditory cues of precipitation, to complement Kerala’s brand image of a water world.

The notes of a place

A smellscape is shaped by the composition, concentration, intensity or strength, and persistence of aromatic compounds in the air. The vocabulary of perfumery can be borrowed to describe the character of smells in places. A smellscape can be thought of as three distinct 'notes' that are unveiled over time. The first impression of the smellscape is provided by the head note or top note, which is followed by the middle notes or heart notes, which are detected as the top notes fade. They linger in the air for a longer period of time, like the aroma of a barbecue. When the middle notes become imperceivable, the base or bottom notes become perceptible. These background smells establish the overall smellscape of a place, such as the fragrance of flowers in parks or the stench of polluted air from automobile exhausts on motorways. Smells can be further classified into families such as Floral, Citrus, and Gourmand, with descriptor subtypes such as fresh, woody, spicy, and animalic, to name a few. Walkways and public squares need to have these notes incorporated into their design.

Composing a scent signature

The art of creating a smellscape involves curating a signature scent for the place that captures the essence of the place. Being constantly in flux, it is challenging to predict and control smells in a smellscape. However, it is possible to amplify or conceal consistent and episodic smells through sensitive design.

When attempting to produce an ambient scent for a location, several different variables must be taken into consideration, including humidity, airflow, temperature, foot traffic, the presence of plant and water features, the existence of artificial odour-producing materials, local preferences and tolerance levels, and many other factors.

People's acceptance of a smell is determined by its intensity perceived as its strength, its quality or character, its hedonic tone, which is its overall pleasantness or unpleasantness, their prior experience with the smell, congruence with the current context as well as their sense of olfaction. The psychological and physiological restorative effects of natural smells from city parks tend to be lesser for rural residents who are accustomed to cleaner and fresher air. People appreciate perceived smells' aligning with their surroundings and are annoyed or revolted by de-contextualized smells. We might enjoy the smell of seafood in a fish market, but it would be disturbing in a park. Identifying and preserving distinct smell zones in a city can aid in the complementarity of a place's sight, sound, and smell.

Olfaction is important in food streets because it is essential to experiencing flavour fully. The aroma of freshly baked bread can help you envision a golden loaf, remind you of the taste and texture of its buttery softness and chewy crust, and can also evoke situated memories of a satiated appetite. In café-lined streets, any source of odour that obscures appetizing aromas including air fresheners, must be reduced. When smells inform pedestrian routes, sweet and savoury goodies direct the way.

It can be challenging to quantify the effects of smells on people's experiences. Most smellscape components are short-lived and dependent on individual or collective perceptions at a specific point in time. Through ‘smell-walking’, it is possible to generate smellmaps, or visual representations of the perceived smellscape. Participants record their conscious perceptions of a predetermined route and describe what it means to them by using objective descriptions such as the ‘fragrance of jasmine’ or by associating it with emotions like delight, despair, or even perplexity. In contrast to smell-walking, participants in ‘urban drifting’ take unplanned walks through urban areas and record their observations through text or drawings. Brain imaging can also be used to assess how smells affect people by highlighting brain regions affected by recognizable smells from a place to which the participant has strong emotional attachments.

Perfume briefs or client descriptions of their desired scent provided to perfumers are typically imaginative and impassioned. A survey of resident preferences in this manner could help designers more effectively incorporate the desired natural scents into spatial design, to encourage pedestrianization, and in turn improve public health, social cohesion and the street economy.

Making sense of scents

Focusing on smellscapes instead of odour nuisance reduction opens up new opportunities to understand how important smells are to human experiences and well-being. A holistic perspective of a place is developed by being conscious of both its pleasant and unpleasant smells. Addressing sensory experiences while designing and planning public spaces would preserve the individuality and identity of places while advancing our understanding of their characteristics. The artful blending of passive and active smells of a place would allow the composition of an olfactory signature, that is unique and appealing to both residents and visitors from diverse backgrounds.

(Ann Rochyne Thomas is a bio-climatic spatial planner and founder of the Centre for Climate Resilience - a sustainability and climate change advisory.)