Re: Why are there odors we know but can't identify?.

Our olfactory senses work via a synergy of the nose and brain. Odor 
compounds enter the nasal passage and stimulate receptors in a certain 
configuration. Although receptors are unique to individual odors, more 
than one odor can can occupy a certain configuration of receptors. Along 
with processing the odor through your nasal passage, you brain incorporates 
context clues to determine the nature of the odor i.e if you are in a 
kitchen smelling an odor, your brain is most likely to discrminate the 
smell among food items rather than for example the odors of gasoline and 
oil you might smell in a machine shop or car repair shop. Hence, at times, 
one might be able to smell an odor but if it is our of context with the 
person's surroundings, they may perceive it differently or have a 
difficult time assimiliating it to their surroundings.