This is not a deviation from settled law with regard to dwelling. If a cop smells pot coming from the other side of an apartment door, would you not consider that probable cause to believe Marijuana is on the other side of the door. If a cop smells alcohol on your breath at a routine traffic stop, he can act. Why the paranoia, just because a dog's nose is more sensitive.
You're not going to get arrested because a seed from a prior owner of the car is in your carpet.