What causes the smell?
Terpenoids.
Most of the smell comes from the idle smoke burning from a joint while it is
being passed or when you are holding a hit in your lungs.
This is why exhaling into a toilet roll with Bounce dryer sheets rubber bound or taped to the end doesn’t work
...(,...:no:...Now they tell me..)
along with techniques like exhaling into a bag or holding the
entire hit in until nothing comes out when exhaling.