A dollar bill.
A dollar bill. - 
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Sarah Gardner: So you've heard of drug-sniffing dogs, right? Well today we read about a new role for canines in place like Argentina -- dollar sniffers. Yes, they have been trained to sniff out dollars to combat the black market in greenbacks.

So it got us thinking: What does money smell like? Dollars are made of cotton and linen, and according to the Treasury's Bureau of Printing and Engraving, different types of inks are used on different denominations. But really the smell is affected by what the dollar comes in contact with -- dirt, sweat and yes, cocaine, acccording to research by the Argonne National Laboratories in Chicago.

To understand all of this a little bit more we reached out to Stuart Firestein at Columbia University's Department of Biological Sciences. Welcome to the program.

Stuart Firestein: Thank you. Nice to be here.

Gardner: Listen I have to ask you: What do you call someone like yourself? What's the official title for someone who is an expert on smells?

Firestein: We call the field the sense of olfaction, is the true word for the sense of smell. So there's olfaction for smell and gustation for taste. But in the end everybody just calls me a smell expert, I'm afraid.

Gardner: OK. There's nothing like "smell-ologist?"

Firestein: No, no. We don't have that one yet.

Gardner: OK. So what about money? Does it have a unique smell?

Firestein: Well apparently so since dogs are able to smell it. I've always thought it did myself personally. You can always catch that, especially new bills.

Gardner: That's right. We talk about the scent of fresh money and you think of people of smelling fresh dollar bills. Well after your hands get on it, isn't not so fresh, right?

Firestein: Picks up all sorts of ugly stuff. So it wouldn't be a bad idea to deodorize it every now and again, I suppose.

Gardner: Now I read that money is basically cotton and linen. Do those have distinctive scents?

Firestein: They're very light. So again I think it's primarily the ink rather than the paper in this particular case that gives off the odor.

Gardner: Dr. Firestein, I'm just curious, how does it work? When the dog smells this money, how does it get from the nose to the brain? What's happening there?

Firestein: It's a principle of what we call molecular recognition, which is a big word for something that's actually quite simple. In the nose of a dog -- way back in the nose of a dog -- and in a person as well, we have small cells that communicate with our brain. On the surface of those cells are little proteins, which we call receptors. You can think of it as a sort of a lock and a key. The receptors, these proteins, are like a lock. And the odors are like a key. And if the odor fits the receptor just right, the way a key fits a lock, it will activate it. And upon activating it, a signal gets sent to the brain.

Gardner: I take it that different scents affect people in certain ways. Do you think smelling money could do something to someone -- in some positive way, some negative way?

Firestein: Well, it makes me feel a lot better. It's kind of like new car small. It just gives you that feeling of prosperity, doesn't it?

Gardner: If you could put a scent on money, what scent would you choose?

Firestein: Oh, that's a good one. Chocolate. Why not make it really good?

Gardner: That's right. Stuart Firestein is at Columbia's school of Biological Sciences. Dr. Firestein, thanks a lot.

Firestein: My pleasure, my pleasure.

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Follow Sarah Gardner at @RadioGardner