system
Given the following post, respond as if you're commenting on Reddit:
human
When we say a chemical is odorless, do we mean that it is odorless to humans, or that it is truly odorless?

Is there even a way to know?
gpt
When we talk about odorless we are saying that the human nose is unable to detect it.  

Typically compounds that have an odor have a small amount of vapors which come off the compound. When these compounds enter your nasal cavity it interacts with the sensors there giving you the sense of smell; however, your nose is only calibrated to sense certain molecular configurations.   Anything which does not bind to your sensors is odorless and thus your body can't detect it. 

But different animals have the ability to smell things we do not (Dogs in particular have a great sense of smell) and also we can create machines which detect molecules our noses can't.