In a German movie theater last month, audience members waiting for the feature wondered why they were seeing people lounging on a beach. After 60 seconds of waves and seagulls, a tag line for Nivea sunscreen appeared, and the scent of Nivea wafted into the theater through the air-conditioning vents.

Later, a survey showed that audience recall of the smelly ad was 500 percent higher than for the scent-free version. Whether moviegoers enjoyed the scent of sunscreen with their popcorn was not recorded. But that’s a number that advertisers certainly recall — and one that proponents of scent marketing love to broadcast.

“Scent will soon be a normal part of advertising and entertainment,” says Carmine Santandrea, owner of a scent marketing company in Santa Barbara, Calif. After circulating the smell of milk chocolate in the vicinity of a vending machine, he says, he saw a “sales lift of 300 percent for Hershey Kisses. That’s never happened in advertising before. Those results can’t be ignored.”

Neither can an odor. While you can turn a magazine page or change a television channel, you can’t avoid inhaling. “That’s the good and bad thing about scent — you can’t get away from it,” says Harald Vogt, founder of the Scent Marketing Institute. “In our environment, everything already smells. The question is how you manage the smells.”

The idea of scent in advertising is not new. Back in 1965, Santandrea created a scented Coke pavilion at the World’s Fair in New York. But science has now given Madison Avenue powerful new tools to fulfill its odorous promise. Today’s chemists, for instance, can capture the scent of a strawberry in varying stages of ripeness by taking samples of the air around the berry with a gas chromatograph. The bigger development, according to Avery Gilbert, author of “What the Nose Knows,” is that chemists can develop recipes for any smell, down to a single molecule.

“There’s a plant in the Sierra Nevada in the summer that gives off a cooked artichoke smell,” Gilbert says. “The Indians knew about it; John Muir noticed it. It’s called Sierra Mountain Misery. I took a sprig and sent it to a chemist and found that the smell comes from one molecule that makes up less than 1 percent of the entire formula.”

Scent marketing has also become more sophisticated because of what we’ve learned about olfaction. Smell may be the least lauded of the senses, but it’s the one most closely connected to our moods and recollections. (The loss of it, called anosmia, can produce tremendous anxiety and depression.) Memories inspired by fragrance are more emotional than those triggered by sights or sounds. In studies, scent-elicited memories cause subjects to mention more emotions, rate them as more intense, and report more of a feeling of being back in the time and place relevant to a smell. Catching a whiff of the perfume your grandmother wore is likely to bring back stronger memories of her — and the feelings associated with her — than seeing her photo.

That can happen before you are even conscious of the scent. That’s because an incoming odor proceeds directly to your limbic system, which handles memories and emotions; non-olfactory perception must go to the hypothalamus and then on to the cortex for further analysis. “Scent goes right to your emotions,” Santandrea says. “And if I can appeal to your primal senses, I’ve got you. That is what advertisers do. If you find that offensive, you have a problem with all of advertising.”

Scent marketing is not limited to products that have an inherent aroma, like Hershey’s Kisses; items such as clothing or stereos have their own universe of “scent abstractions” to brand themselves. Smell for yourself: Walk into the Samsung store on the Upper West Side of Manhattan and you may notice a melon aroma. Westin Hotels envelop guests with their White Tea fragrance. (Now you can buy Westin-scented candles to enjoy the hotel smell at home!)

Extensive research preceded the introduction of those scents. Companies start with a “fragrance brief,” describing the scent image they want to project. Fragrance vendors then create scents they imagine fulfill the descriptions. Because Samsung and Westin are global brands, and there is no globally agreed upon pleasant smell, they had to be certain that the scents would not be offensive anywhere.

“To use something ‘fruity’ and ‘light’ is the best bet for any scent marketing effort that is not connected to a product,” Vogt says. “A good example for a product-related scent is Thomas Pink’s ‘Line Dried Linen’ that smells, well, just like it. If you don’t have such a product, you look at your target audience, what they prefer and use, and start from there.”

Some people find smell advertising offensive, akin to subliminal advertising. But Gilbert has a quick defense. “If a pizzeria is venting out onto the street, and the smell makes you want pizza, is that somehow mind control?” he asks. “Scent is a weird channel that people don’t think about on regular basis. Once it becomes more standardized, people will get over it.”

Maybe they’ll even like it. Stores like Samsung want to forge a fragrance bond that creates positive feelings, customer loyalty and increased spending. Research gives them hope.

One study put a floral scent in an area of a casino over a weekend; gamblers there spent 45 percent more money than on other weekends, while the results for unscented areas of the casino remained unchanged. An Iowa State University study showed that introducing a pleasant scent caused shoppers to have more positive attitudes about a selection of sleepwear, as well as a willingness to pay more. But the scent needs to be congruent with the merchandise; a Lily of the Valley fragrance created the positive reaction, but the smell of Sea Mist, though judged to be enjoyable, didn’t have the same results with sleepwear sales.

That incongruity probably led to the 2006 backlash against scented ads in San Francisco. As part of a “Got Milk?” campaign, ads in San Francisco bus shelters were imbued with a chocolate-chip-cookie aroma. The idea was to make people crave milk. They didn’t. Complaints poured in, and the aromatic milk ads came down after just one day.

Commuters just didn’t understand why they would smell baked goods out there, says Rachel Herz, a visiting professor at Brown University and author of “The Scent of Desire.” “They’re in a bleak bus stop and they’re smelling something that doesn’t fit,” she says. She warns that people tend to judge unexpected and unfamiliar smells as unpleasant. “Our interpretation typically jumps to the negative,” she says, and that’s especially true post-9/11, as people are still sensitive to an unusual stimulus of any kind.

Even with all the ongoing olfactory research, much about odor remains mysterious. Chemicals with different structures may smell similar, while those with nearly identical structures can smell completely different. That’s a particular challenge to scent manufacturers trying to design the perfect scent. “If you take a novel assortment of odorous molecules, we cannot predict what that will smell like,” says Northwestern University neurology professor Jay Gottfried. “If we mix amyl acetate — a banana smell — with eugenol — a clove smell — there are no rules to say how the mixture will be perceived.”

Gender and experience, context and memory determine how an odor molecule is interpreted. When Herz had subjects sniff something identified as Parmesan cheese, they liked the smell. A week later she presented the same odor, telling subjects it was vomit. They found it revolting.

With so much ambiguity and sensitivity surrounding our olfactory systems, scent marketers have considerable responsibilities, Vogt says. They should not put their products in public spaces like bus shelters or spritz consumers without their invitation. And even though reputable scent marketing companies in the U.S. use approved fragrances, Vogt acknowledges safety concerns with foreign products; the Scent Marketing Institute is now establishing industry standards.

Even so, companies know there will be complaints — Vogt recently received an e-mail with a subject line that read, “You are making us sick.” A vocal population considers itself chemically sensitive, and scent marketers have already become a target elsewhere. Halifax, Nova Scotia, has declared itself a completely fragrance-free city. “In some Scandinavian countries, they’re legislating against letting vaporous scents into the air,” Santandrea says. “We’re going to have legislation against us. But if the scent doesn’t cling to you, we have a right to do it.”

Santandrea insists that scent marketing helps consumers by giving them information. “We’re democratizing scent,” he says. “Shopping is merely hunting, and in the past when we hunted, we used our noses to inform us of what we were coming to.”

At least for now, practical limitations remain. With many different smells mixing in the mall, the results could quickly become unpleasant. After 15 minutes or so, the nose adjusts to a scent and stops perceiving it. And when you go from one scented store into another, the fragrance of the second store may seem distorted to you, or hardly smell at all.

Still, efforts to introduce scent to everything seem irresistible. A few years ago we almost witnessed the release of iSmell, a “personal scent synthesizer” that would have released odors from scented Web sites and e-mails out of your computer. Although the company involved fell victim to the dot-com bust, the technology is available.

Motorola has a “smell-o-phone” in the works (so you can look forward not only to hearing the conversation of the person next to you but to smelling it too. Scent-a-Vision should be available in the next two or three years, according to Santandrea, who has invented an appliance that synchronizes scent tracks with movies. Some techno clubs have hired ODO7, an “aroma jockey,” who mixes smells onstage to add a “third dimension of entertainment.”

Those kinds of applications, Gilbert says, likely hold the key to scent’s future. “There will be a breakthrough in a popular culture application — clubs, concerts, maybe scented artwork,” he says. “Maybe then there will be a quiet revolution and scented ads will be no more ominous than billboards in Times Square.”

This week, days before Friday’s opening ceremony of the Beijing Olympics, cannons and rocket launchers by the thousands will be trained on the Chinese skies. In the cross hairs: the clouds.

This is latest of China’s many efforts to control the weather. China is probably the world’s largest practitioner of cloud seeding, spending about $90 million a year. Last April, it claimed a major weather victory after seeded clouds deposited a centimeter of snow on the Tibetan mountains. Now, eager to ensure rain comes before — not during — the Olympics, the Beijing Weather Modification Office plans to seed the clouds that float by beforehand, hoping to wash the pollution from the air and wring out any event-delaying precipitation.