This depends on whether you are an active smoker or a passive smoker. Also the frequency and the number of cigarettes smoked has also got to be taken into account. In general for active smokers the nicotine remains in the blood for 2-4 days However for passive smokers it can remain in the blood for a longer duration.
It depends on what type of test you are going to use to detect nicotine and whether or not he person has been smoking occasionally or continuously. For urine test it can only detect up to a maximum of 20 days, while in hair tests it may detect nicotine presence from 60-90 days.