The next time you enter a hotel and are greeted with a whiff of something unfamiliar — fresh, addictive, or delicious — know that it’s likely intentional. It’s not there to mask something less savory. Or to lure guests into a gift shop where it can be purchased as an 8 oz. poured candle. (Though that may also occur.) Instead, the scent is said to be there to evoke a feeling, awaken the senses, and to, above all else, create the impression that staying in this particular hotel is an experience like no other.

“Scent and smell are a big part of how people perceive a space. The idea of hotels tapping into that is to get people to remember their stay,’’ explains Carly Fowler, a New York-based account executive/project manager at Air Aroma, an international fragrance development agency that creates custom scents and distribution systems.

Fowler, who has several Boston-based accounts, has overseen the creation of fragrances that evoke springtime and melting snow on the Common (willow leaves, blossoms, and sweet freshness of orange) for the Four Seasons, and reflect the rich heritage of afternoon tea at the Taj (a blend of green, white, and red teas — romantic and robust).

“Fragrance helps to emphasize the overall brand message, while also creating a luxurious environment and feeling,’’ she says. “The same way influences in lighting or other amenities might.’’

It may seem simple, but the effect is two-fold. On a surface level, it’s a branding technique to create a unique environment, a sneaky immersion that infiltrates the memory in ways silky soft sheets and tinkling pianos in the bar cannot.

“People often think they’re falling in love with the scent of a hotel, but really they’re falling in love with the experience,’’ says Dawn Goldworm of New York-based experiential fragrance agency, 12.29. “When a client is away from the brand or hotel, living their normal lives back at home, [the scent] creates a touchpoint. When they open a closet after they took a scented sachet we left in the room or light a candle they bought at the hotel, they get a whiff of the experience they had. It not only reminds them of the hotel, it brings them back there.’’

Dawn and her sister Samantha Goldworm are the minds behind 12.29 — Dawn, the vision, Samantha, the nose. Together they weave what they call “emotionally charged olfactory wonderland(s)’’ through custom scent experiences for the likes of Valentino, Lady Gaga, and Art Basel. On the hospitality side, they work with brands like the Independent Collection (which includes the Boxer in the West End) and Yotel, the trendy minimalist Millennial hotel chain set to open in its first Boston location in the Seaport this summer.

A new scent is created through an intensive study of their client, their visual approach, their design strategy, and their language. “It’s a deep dive,’’ says Goldworm, who also experiences the hotel by staying overnight and spending time in the common places. “It takes about four months, but the process, interestingly enough, has nothing to do with smell. And not at any one time do I ask them what they think it should smell like.’’

For Yotel, 12.29 wanted to reflect the “super simple, very user-friendly’’ brand design and mantra. They broke down the message into four categories: refresh, relax, sleep, and connect. The final result is a juicy, wet combination of cassis and cucumber, with green, tingly Shisho mint from Japan and soft Ozone notes “to make the scent comfortable.’’

Air Aroma’s process is a similar holistic approach, with hands on deck across internal design and marketing teams and psychologists and perfumists. Fowler says they can go through several rounds of fragrance samples before declaring a winner, with a timeline “anywhere from four weeks to six months to a year.’’ The chosen fragrances are then pumped via Air Aroma-made Ecoscent diffusers through hotel’s HVAC system across common meeting spaces, like the lobby or the spa.

“Because we’re in the luxury sector, we want to create a subtle effect,’’ she explains. “The fragrance will be noticeable, but it will blend into everything else happening in the space. You wouldn’t want to walk into a nightclub, and have the lights be too bright. A scent should have the same impact; nothing should overpower each other. Everything should be in balance.’’

Both agencies create fragrances that are IFRA-certified, meaning they meet regulations for allergies, toxicity, and other risks. Engagement in fragrance experiences within guest rooms is made to be optional through drawer liners or scented stationery.

“It then becomes the choice of the client to engage,’’ says Fowler. “You have the choice to set your lighting or put on music or watch TV when you walk in a room, we want it to be the same with scent. It’s your choice, as it should be.’’

The second factor to consider is the longevity of a brand’s message transferred through scent. Both the Goldworm sisters and Fowler note that scent imprints the brain differently than other sensory-created memories. A custom scent not only is a fun, luxurious feature, they insist, it’s an effectively long-lasting impression that’s been scientifically proven.

“The parts of the brain, called the smell cortex, that decode smells in our environment are evolutionarily primitive (paleocortex),’’ explains Jim Schwob, Bates Professor at Tufts University School of Medicine. “They connect directly to parts of the brain (like the amygdala and hypothalamus) that the brain uses to assign the emotional importance to smell stimuli and whatever else is happening to the individual at the same time. For example, the smell of freshly baked cookies and a hug from your mom, or, from the other side, the smell of bad food and the experience of being sick to your stomach.’’

Additionally, adds Schwob, the smell cortex is directly connected to the part of your brain that forms memories from events (the hippocampal formation), thus making scent a powerful marketing tool. He continues, “It is well-known that marketing strategies try to take advantage of the emotional connections.’’ (Think: “the new car smell, when trying to make a sale.’’)

Consistency is also a consideration across hotel chains — like Yotel, or on a more consumer level, the Westin — where each location features the same scent. Yotels all over the world will smell of juicy berries and Ozone; Westin hotels will always smell of woody cedar and white tea. The idea being that brand identity translates to brand loyalty through scent recognition.

“If you think about it, the Nike swoosh doesn’t change because they launched in Japan versus Brazil,’’ says Goldworm. “Large brands are able to create loyalty through consistent experiences. You gain a deep emotional experience with a brand through those consistencies. Scent is the same way, deepening this. Scent experiences will evoke emotional ones.’’

Rachel Raczka can be reached at rachel.raczka@gmail.com.