Will cigarette smoke stay in the blood stream how long?

Cigarette smoke never enters the bloodstream, and so the question cannot be answered as asked. Cigarette smoke contains over 4,000 individual chemicals, many of which are gases which may cross the blood-gas barrier of the alveoli and enter the blood stream. Many of the particulates may similarly be trapped in the mucus of the trachea wherein other compounds may be leached from the particles and eventually enter into the blood-stream. The toxicological fate of each of these compounds is unique for that compound, and the elimination rate is therefore different for each. Various compounds may be sequestered in other tissues where, during times of biological stress, or other biological changes, be again released into the blood. Without knowing which specific compound is of interest, it is impossible to provide a general answer of "how long" the "average" compound may remain in the "blood stream."