Smell is a base human faculty, yet it was one of the last understood by scientists. Which is perhaps why it lags behind the rest when it comes to sensory experiences.

Humans have about 350 different olfactory receptors. Most exist in the nose, but more than 15 have also been found in skin cells. These receptors are among the most evolutionarily ancient chemical sensors in the body. They’re capable of detecting a multitude of compounds, as well as particles floating in the air. When these ‘smells’ reach the nose, a biochemical reaction occurs and sends a nerve signal to the brain, where it is identified as odour.

But most interestingly, smell is the only sense that’s routed through the part of the brain that directly handles memory and emotion (known as the olfactory bulb). And for obvious reasons, it’s this property of our smell sense that marketers want to take advantage of.

The race to find the holy grail of olfactive technology – devices that elevate smell to the same perch as sight and sound – has no obvious frontrunner. It never has. That’s not to say there haven’t been strong contenders. Quite the opposite. Over the past century, inventors, scientists and the curious have conjured up ways of enriching our lives with synthetic scents. Although entertaining, the science often remains incomplete and superficial. This article is a collection of smaller articles, split into two parts, which journeys through the history and future of olfactory technology. Although topics such as video games, music and food – including eating by breathing or Heston Blumenthal’s atomised sweetshop mail – were worthy contenders, the focus of these mini-articles will be on the following four themes: Media, marketing, medicine and crime, respectively.

Let’s begin.

Media and technology.

Smell is sometimes referred to as technology’s ‘missing sense’ – and it’s not hard to see why. Our online world is a busy media patchwork of visuals, sounds and words. And although try-out opportunities have been aplenty, smell is yet to be invited to sit at the cool kids table.

Virtual Reality (VR) and Augmented Reality (AR) are already pushing the technological boundaries of sight and sound. It’s a step into the fourth dimension, a new fully-immersive reality. Presently, however, there’s a limit to how immersive this technology can be. With the absence of taste, touch and smell, VR and AR are three senses short of a hand. The holy grail, therefore, is tech that emulates all five of the human senses – to send consumers down the rabbit hole, through the wardrobe, into a time portal.

Talking of going back in time, enter Samuel “Roxy” Rothafel – a film industry pioneer who is famed, amongst other things, for experimenting with smell in media. Forest City, 1909: Rothafel screened the Pasadena Rose Festival, and dispersed paper streamers, perfumed in rose oil, filling the auditorium with an air of fresh flowers to match the visuals.. This puff of floral nostalgia proved popular at the time, attracting new audiences and gaining a name for himself in showmanship.

Post-Roxy’s rose-infused work, it wasn’t long before others had expanded the remit. Smell tech found a place in the cinematic experience. Swiss entrepreneur Hans Laube premiered Scentovision at the 1939 World’s Fair. He hoped that piping odours to each seat would have more success than pumping smells through air-conditioner ducts. Accompanied by a 35-minute film, Laube puffed scents of lilac, cedar, honey, sausage, rose and tar throughout the feature. The audience’s response? They thought it foul.

Fifteen years later, Mike Todd Jr created Smell-O-Vision for to the mystery-comedyScent of Mystery. This film was to marvel audiences as the first in which smells revealed certain plot points to the audience. But, it was beaten to the punch and became arch rival to AromaRama in “the battle of the smellies.”

On December 2, 1959, Walter Reade Jr. released Behind the Great Wall – a travelogue through China accompanied by AromaRama. AromaRama was created by Charles Weiss, an inventor who wanted to bring 72 odours of China to the padded red chairs of a New York City theatre. Weiss believed that “smells are surer than sounds or sights to make the heartstrings crack,” and made sure the production was released three weeks before Scent of Mystery to ensure success in America. Which worked, to some degree. Some of his audience members loved the burst of oranges that filled the air at the very moment an image of an orange being sliced appeared on screen. Others, however, described the process – as well as its competitor Smell-O-Vision – as a “desperate attempt in the 50s to regain customers lost to television… Neither system proved popular, although technically they were both successful.”

Six years on, piped smell took the back bench as 3M introduced ‘scratch and sniff’ to the scene. This technology quickly evolved, causing the rise of scratch and sniff stickers in the late 70’s – a gimmick that became hugely popular and remained so ‘til the mid-1980s. In addition to stickers, this technology has been successfully used from vinyl covers to comics, CDs and direct-mail marketing pieces. This popularity proved smell technology had an audience, and a place in media. For Director John Waters, this was enough evidence to brave taking smell back into the movie theatres with his show, Polyester. Audience members were given scratch and sniff cards and prompted by on-screen cues to inhale scents of glue, pizza, gasoline and more as the film played on. Waters labelled this gimmick as ‘Odorama’ and advertised it with the tag “It’ll blow your nose!”

But this valiant attempt was destined to join the ‘close, but no cigar’ club – and after the 1980’s hype, it collected its badge and took its seat next to those who’d come before.

By 2000, DigiScents was leading the charge – focusing on dynamic, adaptable devices that communicated over the Internet and would change the way we use the web. Founded by Joel Bellenson and Dexster Smith, DigiScents released the iSmell in 1999, describing it as a “scent speaker” for the home. The “speaker” encases a scent cartridge consisting of 128 odours in oil form which are heated, and dispersed, by a small fan when triggered by the computer. Despite receiving an encouraging response from audiences and a $20 million investment from various companies, DigiScents, and the dream, died a year later.

“The sense of smell is kind of a close and personal thing,” notes Columbia professor Firestein, who served on DigiScents’ scientific advisory board. “It’s not clear whether people want that kind of invasion of their private space.”

Today, cinemas, theme parks, restaurants, fright festivals and cinemas have decided to bring a slightly different tact to smell in theatre. Modern examples include inviting guests to walk through corridors recreated to mirror an earthy forest world. Complete with scented foliage, the sound of scurrying wildlife echoed through the trees and pine infused cocktails once you’ve reached the end of an authentic bark path – all before watching the Lion, the Witch and the Wardrobe on logs under a star dotted sky. Because it can target an audience like no other sense can, smell’s place in media is an important one. However, rather than trying to deliver a new punch of smell every time the scene changes, creating an ambience in keeping with the overall theme seems to tug on the heartstrings more than different whiffs floating up from under the seat.

Olfactory Marketing.

Smell is the sense most linked to our emotional recollection. Seventy-five percent of emotions are triggered by smells linked to pleasure, well-being and memory. Being able to tap into this subconscious trigger and link directly to a brand or product would be a powerful marketing tool.

Most notable was in 2012 when Dunkin Donuts deliberately targeted city buses in Seoul with coffee aroma every time a branded ad was played over the speakers. The result? A 29 percent spike in sales in locations near city bus routes.

With promises of elevating RIOs, marketers have continued to jump on the smell technology band wagon. Rolls-Royce developed the scent of the 1965 Silver Cloud to spray under the seats of other models, recreating the smell of a classic Roller. Jorvik Viking Centre in York emitted authentic 10th-century urban odour.

Businesses have successfully influenced buying behaviour with smell, but only when the scent corresponds to both the product and its general surroundings. It’s this focused deployment that makes the campaign familiar to its intended audience – keeping a clear stream of thought that subconsciously plucks at the consumers’ heartstrings. According to a study by Nike, intent to purchase increased by 80 percent after adding a scent in-store. Another successful experiment saw coffee purchases increase by 300 percent at a petrol station after pumping the smell of coffee into the forecourt. Now, there is every chance this 300 percent increase was due to an undocumented caffeine-hit epidemic, though that seems unlikely.

Our olfactory receptors can distinguish 10,000 different smells. Each scent travels immediately to our brains, bypassing the process our other senses endure. This is the core reason why scent marketing can be so effective. By introducing olfactive technology, marketers can cut through the sea of visual content, targeting instead the sense that triggers emotions and impulses. Although, be warned: This sensitivity comes with its own hazards. In 1987, a marketing strategy by Baltimore Gas and Electric Company led people to mistake a scratch-and-sniff card, scented with methane gas and left in unopened envelopes, for real gas leaks. This triggered a wave of false alarms, causing chaos amongst the emergency services and unrest in homes up and down the country.

Olfactory illiteracy and subjectivism are also reasons why scent marketing continues to be a hard sell, warns Harvard Professor David Edwards. Where one person might smell coconut and dream of parrots, cocktails and crystal blue seas, others will think of a bounty bar. Another group will smell something but won’t be able to identify it, and there’s a small percentage who won’t be able to smell it at all. This might explain why smell-gadgets, such as SensorWake – an alarm clock that slowly wakes you with a puff of scent – choose to use only the ‘undeniable’ smells of coffee, croissants, bacon, candy and mint. But even with these ‘safer’ options, one bad cold and your consumers will need more than a nose tickle to get them out of bed.

When done right, olfactory marketing can bolster a brand’s ROI – but it doesn’t always smell of roses. When scents become muddled, unexpected or overwhelming, it can trigger customer friction. This in turn can encourage consumers to feel negatively about a brand or cause people to switch off altogether. Switching off is also prompted by our ability to get bored of smells easily. Think about the last time you walked past a bakery. Although the smell of fresh bread wafting down the street may be the reason you entered the shop, by the time you reached the till, the bakery will have won over your buying-impulse but the smell will have been lost.

And it’s this that marketers want to take advantage of. If they can use targeted smell technology to cut through the everyday; awaken memories and trigger the impulses that follow, even for a second, they’ll have a leg up on the brands only looking to please through crafted words, loud noises and pretty pictures.