system
Given the following post, respond as if you're commenting on Reddit:
human
Why do things keep smelling? Can odor get "Spent"?


I was handling a key and noticed my hands smelled like metal after. I wondered how long this key has been around and was curious about the fact that it still had a smell. I imagined the "odor particles" coming out of the key and wondered if they ever get spent... (and if there even is such thing as an "odor particle")

Thanks beforehand!
gpt
The smell of metal on your hands after handling keys, coins, etc is actually the smell of your body's natural oils on the surface of your skin reacting in a small way with the metal. Chemical by-products are released, some as vapours that you can smell.

Once you remove the metal, the smell lingers until the chemical reaction has 'used up' the available metal atoms and the smell disappears.