Everything has a unique chemical signature. Every body, every place. When you smell home you’re sensing all the chemical traces that make up the place you grew up. When you smell your mate, you’re smelling the unique combination of their body and the microbiome of their skin.

The unique smell of a city is something that my Synthetic Aesthetics partner, Sissel Tolaas, has been interested in for a long time. Yesterday in her lab I got to smell her recreations of the smells of Paris–the corner bakery, dog poop on the sidewalk, old rusty cars, cigarettes and perfume, sun on the street after heavy rain.

She’s analyzed the smells of several cities, creating scratch-and sniff maps of Mexico City, beautiful perfume bottles filled with the smell of Berlin neighborhoods, and smell profiles of cities as different as Vienna and Kansas City.

Yesterday I also learned via @bldgblog that DARPA is seeking proposals around a similar project, collecting and cataloging the normal chemical traces and smells of cities in order to be able to rapidly detect an airborne chemical attack. Sissel maps city smells to explore the boundaries we create in cities, to repackage and recontextualize the sometimes gross smells we encounter in our urban environments, to question the language we use to describe smells. She’s quoted in a great Edible Geography article saying:

Challenging people to use their noses gives them new methods to approach their
 realities; it doesn’t matter whether they smell a so-called bad or good smell. What counts
 is that they rediscover their own surroundings in that very moment–be it other human
 beings, places, the city — and start to approach it differently.

I’m curious about what the effect of the DARPA project will be. Will people become more aware of their smell environment when more fine-grained and technical information is available about the spatio-temporal distribution of chemicals in the city air? Will smell information become just another facet to organize our fear around? The data is likely to be fascinating either way, an “X-ray of the air” that we can use to better understand the air that we breath every day.