Lesson 11 - Smoking

Sherlock is an addicted to ciggaretes, John tries to avoid Sherlock from smoking, but he just can't.
Sherlock wasn't an addicted until Mycroft gave him a ciggarete for Christmas "A Scandal in Belgravia".
Until Sherlock became an addicted, he just took nicotine patches (three at a time) "A Study in Pink".
Sherlock is not exacly a smoker in "Hound of the Baskervilles", he is a second hand smoker.