Why is it easier to smell objects if you breath on them first?

Factual Questions
1

OK, a bit of background. Here in Hong Kong, people are money-crazed. (What’s the definition of a queer in HK? Someone who prefers sex to money.) And one of our favorite pastimes when no-one is looking is to get some freshly printed banknotes and smell them. MMMmmmmmmm. The HK$1,000 bills smell best of all (they’re worth about US$130), and the lower denominations smell good, but not quite as good. The HK$20 bills (US$3 roughly) are a bit boring, aroma-wise.

Anyway, I can’t help noticing that the smell is accentuated if you breath heavily on the bill first. In fact, it works with most solid objects - breath on it, and you can smell it better.

Why?

My hunch is, the moisture and warmth in your breath brings out the molecules that impart the smell. Walk in the woods after it rains in the summer, and your nose is regaled with the smells of rotting dung, leaves, etc. Not so during winter.

But is there a scientific explanation?

2

grin, thanks for sharing… I thought I just had to worry about people with dirty hands touching my bills…

Like you, I’d like to hear from a chemist on this. In the meanwhile (in order of importance):

  1. Blowing on many things is liable to increase the circulation of molecules that can be smelled by your nose. (We were taught in chem class not to smell a liquid by sticking our noses in, but to wave our hand over the top of a beaker towards our nose.)

  2. Heating objects tends to make them smell. Your breath on a thin piece of paper, for example.

  3. Putting your hand’s body oils on something volitile moves part of that scent to your hands, where it’s much warmer.

  4. Moisture reactivates a limited number of things that are just below the amount in the humidity.