Olfactory receptors are specialized sensory cells that are located in the nose. They are responsible for detecting and identifying different smells. When we breathe in air, the air molecules enter our nose and dissolve in a layer of mucus that covers the olfactory receptors. This activates various olfactory receptors, which send signals to the brain that are interpreted as a sensation of smell. The brain then uses this information to identify the specific smell that we are experiencing. There are many different types of olfactory receptors, each of which is sensitive to different types of molecules. The combination of olfactory receptors provide the experience of a wide range of smells. We have evolved these receptors to determine the presence of specific chemicals to ensure health and wellbeing, but we can now use the receptors for enjoyment and understanding, beyond the physical requirement to sense dangerous materials and compounds.
Scent works at distance like vision and hearing, but scent has another dimension, in that the simpler compounds seem to last longer in the environment to be experienced than more complex compounds, which deteriorate quickly. Most scents are complicated and have multiple compounds, and the proportion of these creates a signature smell, so two materials may have similar chemicals, but one has more than or a slight variation from the other, then the smell will be different, if the human nose can recognize the compounds. We are able to smell many thousands of chemicals, but other species can sense more, so it is understandable that some animals will have a better or different understanding of the elements in the environment than we do. Nevertheless, scent is an extremely important sense that transmits information, but it is commonly overlooked for first, vision, and second hearing.
Through evolution, we have developed the sense of smell to detect materials, however we can now use the sense to convey information, as well as perceive materials. We are able to create and capture smells through perfumes, essential oils, reduction, and other methods. These can be used for specific knowledge, especially along cultural lines. Some groups have special meaning associated with certain smells, and this knowledge allows us to use these smells as signals or warnings.
Because of the bias toward vision and even hearing, we do not often think of using smell in design except perhaps cooking. However, as architects, we should. Scents and memories are very closely related. When we smell, we sniff the scents through our noses. In our nasal cavities, we have chemical receptors called the olfactory receptor cells that transfers the smell from your nose to the brain through the olfactory bulb which is responsible for analyzing smells in the brain. Due to the closeness of the olfactory bulb with the amygdala and hippocampus (the regions of the brain responsible for retaining memories), many smells overlap with memories, and memories can be easily triggered with a specific smell.
There are cultural aspects to utilizing smells in interior design, as well. For every different city and region, there are common smells that the area is accustomed to, and there are many different smells that the area or community has never grown fond of. Knowing each community is essential to create living spaces that will be liked. For example, a person from Chicago, Illinois may be accustomed to the smell of their environment and genuinely enjoy the aroma of the streets, but a tourist from Atlanta, Georgia might smell the area and dislike it immediately. Preference of smells pertaining to a community can be as specific as between counties or cities in the same state or as general as between nations or ethnicities.
Smell is similar to taste, touch, hearing, and vision in the case that the sense provides information about an object or space. In addition, smell is similar to vision and hearing because it can be transmitted over a distance. However, smell is different than the other senses in that it can determine precise chemicals, and the brain must rely on memory and intrinsic knowledge to determine what those chemicals mean. Other senses, besides taste, can provide an understanding on the size and motion of an entity, but smell and taste cannot.
Because scent has such charged meaning, one should use the sense to either attract or repel, although it can also be used to create moments of variation in a space. However, it is important to limit the amount of the odor to ensure it does not annoy or put off the user. Because smell carries memory and specific knowledge, it should be limited in scope to defined locations and groups. For example, rich floral perfumes are appreciated by older generations, but the younger population tends to prefer simple and sometimes artificial odors over the complex flowery scents. So, the designer must define the target audience then release this at the specific points. Even those that appreciate a smell will grow tired of it over time.
We can describe smell by a few variables. These include, complexity–how many chemicals is it composed of, volume or amplitude–how much of this scent is in the space, qualitative value–what does the scent mean and to whom, and finally, frequency–is this a smell that occurs once a day, or is it something that you only smell in certain season?
Smell should be used sparingly. A scent, even a pleasant one, can be overpowering with too much exposure. As always, start with none, then add smell lightly and build up. If the scent is persistent, it should be muted and low. If the scent is localized, then care should be taken to ensure the smell is strong enough to be experienced, but not too strong as to be sensed throughout a space. If care is taken, it is possible to have many scents in a space, and with practice, it is possible to combine multiple scents across a space to create a sort of chord. Again, smell is the sensing of a combination of chemicals, and it can be like magic, combining multiple scents, hence chemicals, to create a new form.
For smell, designers can play with the simple scent itself, but they are encouraged to explore meaning and memory in the chosen odors. Doing this will unlock more than an aesthetic experience, it will allow a psychological journey based on perceptions and understanding. This may require the designer to research the user’s history, but also the user’s culture. Are there smells that are pleasant to some but disagreeable for others? Of course, and knowing what these are will allow the designer to avoid a false step in the design process, as well as the exposition.
To showcase smell, we need to use a variety of techniques, but in each, the scent is not long lasting. The reason for this is that smells fade way or are composed of volatile chemicals that decay over time. As time progresses, a scent diminishes. So, useful materials for providing smell experience include perfumes, applicators, naturally occurring aromas, and manmade aromas, such as baked goods. However, these smells must be replaced or replenished throughout the length of the exposition.
Scent can be broken into chemical type, amount present, and extent experienced. Furthermore, the smells can be classified qualitatively by level of satisfaction, cultural meaning, and memory. There may be other ways to classify scents, but using all six of these provides hundreds of variations just with one scent.
Smell is a strong tool for design because it is so tightly wound with our psychology. It could very easily be the first sense biologically as it is working with the raw chemicals, no interpretation or structure needs to be applied to allow it to convey information. Because of this, smell can hit like a sledgehammer and provide experience or recall of memories to change the state of mind of the user. Furthermore, we are able to create memories with specific scents through repetition of experience and associating information or meaning with these repeated trials.
The types of smells are determined by the combinations of the chemicals sensed by our many receptors. The more receptors we have the more smells that are possible, because we not only understand scent from the triggering of one receptor, but also with the combination of multiple receptors. We cannot say there are an infinite number of smells, but there are certainly millions of combinations. Each combination can hold its own understanding, so there is an entire language that can be conveyed just through smell. The question is: how many people are able to understand this language, and how does it change from person to person or location to location?
There are two methods of smell: passive acceptance, and active communication. We use the passive form to understand the world around us. So many things provide a scent, and our evolution and biology allow us to understand many of these, and our experience allows even more. However, active communication allows us to tell the world our stance. This can be a very basic form such as through pheromones, or they can be through the use of detergents and perfumes. How do you show someone you care? Do you clean up for them? Do you bring flowers or food? All of these have scents, and these scents mean something.
If used carefully, smell is a wonderful addition to the experience of the senses. To rely on only the visual is banal, and a quick hit of aroma can enliven a design, or a consistent, subtle perfume can put our minds at ease.
To use smell for design, we need to analyze what ambient smells are in the space, limit those odors that are not pleasant nor are able to augment the design intentions, then we need to determine what scents are appropriate for the design, and finally develop how the smells are imparted. In a basic way, we can partake of smell through our nose, through our mouth, and also in conjunction with taste. In fact, much of the taste experience is actually smell. As we determine the scents to use, we need to employ our strategy of starting from nothing and building up. Again, smell can pervade space, and it can annoy some much more than a visual or aural stimulus if overused and consistent.
Smell can improve a design by scents’ connotations and the simple odor produced. We can stimulate the user by the providing positive and negative smells, which will affect mindset. However, if we can research or understand the user, we can use smells that affect the user emotionally through memory and familiarity. This is not crucial, but to have scents that have personal meaning can really propel a design in the mind of the user. Because it is so tied into our brain with memory, we can create much more of an impact with it, compared to other senses, if used properly. To use it properly, we must be subtle and with intention.
If we create a design using only smell, we would have an ever evolving space without orientation, and those more complex scents would pass and fade faster than the simpler smells, because of degradation and size of the compounds. We cannot use smell for spatial definition other than general boundaries, and instead, we would use it to affect the point of view or outlook of the user. Although this is an interesting experiential possibility, it may not be a good choice for day to day use, without the other senses. However, there is no reason not use it in conjunction with the other senses.
If we were to not incorporate smell in design, we would have a very flat experience. Although most traditional design does not think about scent in relation to the project, it is crucial to create a more rounded experience, even if the smells are coincidental and unrelated to the design intent. However, opening our design process to the sense allows us to have direction and strategy to have a more cohesive design. To not have smell, we would have a much more uninteresting installation.
Beyond the typical use of smell, we can use it as an alarm or notification. It could be much more enjoyable to understand it is time through the odor of coffee or magnolia than a buzzing alarm. We can also use scent as a marker so that one can find their way around a complex space. For example, we can have the cleaners or a air freshener that smell like jasmine in one area of a hospital, thyme in another, and other similar scents by department and floor so as to give the user an understanding of place. Again, we cannot orient with scent in a single space, because it broadcasts throughout a certain area, but because it travels through a given space, we can mark each of these spaces with their own scent. Furthermore, it is possible to have scents match or align by floor, to intuit the level of building.
We can also use smell as part of a retrofit or renovation of a space. Simple changes in cleaners, furniture, and textiles, or other items that accept and hold scent, can change the mood of a space. This should be done with a purpose in mind. Although many choose the items to include in a space by availability, these really affect the spatial experience. Can we have an objective when selecting these elements, beyond the visual or the pragmatic? The more we do, the more cohesive is the design. Where possible, we should design to the highest and best use.
There are many methods and technologies we can use to provide a scent sensory experience, and the designer should not ignore smell as part of the design. Although it might be difficult in the current design field to envision the use of smell, with the use of electronics, actuators, and traditional methods, we can provide the richer experience that the phenomenon of smell and memory affords. Out of all of the senses, smell is one of the most successful in integration with technology, especially deploying perfumes with servos and hardware such as Arduino.