Heroin

Smoking 4: Heroin in the air sacs of the lungs

The heroin molecules and the oxygen from the air arrive in the alveoli, the air sacs of the lungs. The heroin is easily absorbed there into the bloodstream.

In chasing, the user inhales and exhales several times, causing the heroin molecules to enter the bloodstream in repeated waves.

A small proportion of the molecules are not absorbed, and these are exhaled from the lungs. If the heroin is smoked in a cigarette, the user ingests some nicotine as well.