Instead of putting my nose near the Hose, I usually look down the nozzle at arms length ( to make sure no prank has been setup, you know, the one where you stuff a napkin in the end of the nozzle... )
When making sure the nozzle is clean, I usually wipe the tip of the nozzle, Diesel stays oily, and gas dissapears quickly.
Or, to upset the enviromentalists,, you can put a drop of fuel from the nozzle on the ground, and Gasoline will evaporate clean, or nearly so, and Diesel will leave an ugly oil type stain.
My $. 02
MerrickNJr