When inhaled, the active ingredients of cannabis are absorbed almost immediately into your bloodstream through the lungs. Peak brain concentrations, coinciding with the effects you feel in your body and your mind, occur within seconds to minutes and the effects can last up to 6 hours.*
When we inhale, air—or cannabis smoke or vapour— it enters through the trachea and passes through the left and right bronchi. These divide within the lungs, like branches on a tree, into many bronchioles. At the end of each bronchiole are tiny air sacs, known as alveoli, that look like a cluster of grapes. The alveoli—of which there are 300 million in our lungs—expand like balloons and fill with air when your chest expands. The walls of the alveolus allow the exchange of gases between your breath on the inside (oxygen) and capillaries that wrap around the outside of each alveolus (carbon dioxide). The carbon dioxide is then exhaled through the trachea, nose, and mouth, while the oxygen-saturated blood in the capillaries courses through and nourishes the body. Cannabinoids in the smoke or vapour are also absorbed into the blood in the capillaries.
The absorption of cannabinoids—based on subjective experience and concentrations in the blood— appears to be similar whether cannabis is smoked or vapourized.