Companies spent $50 million to $80 million on scent-related marketing in 2006, says Harald Vogt, founder of The Scent Marketing Institute consultancy and researcher. That includes spending to fill stores and hotels with customer-pleasing aromas. Vogt predicts spending will pass $500 million by 2016.

Boosting the trend is improved technology for more creative, cheaper and longer-lasting fragrance-based ads, says Bob Bernstein, president of Scentisphere, which supplies scented coatings to marketers and printers. While the bouquet from past perfume-laced magazine ads dissipated quickly after the strip was pulled, he says, scents now can be released with the rub of a finger, last 20 to 30 seconds and be re-activated for years.

"As (scent marketing) technology becomes more flexible, we've started to use it more," Ruffolo says. It helps that companies like Yankee Candle offer more information about scented products, such as what "Christmas cookie" candles would smell like.

But scent can work in emotional ways as well.

Verizon saw it as a way to add fun to the launch of the new phone, spokesman John Johnson says. At the Yankee Candle stores, "Scent is integral to the customer experience — it creates the atmosphere," Ruffolo says.

At least one scent ad failed the sniff test, however.

In December, the California Milk Processor Board gave several San Francisco bus shelters a chocolate chip cookie aroma in a Got Milk? promotion. But the Municipal Transportation Agency ordered the ads removed after complaints from advocacy groups worried the scent could trigger allergic reactions, MTA spokeswoman Maggie Lynch says.

The agency didn't have enough warning to do "due diligence" for consumer safety, she says.

"We're a very green city. We are concerned about sound ecology in everything we do."