Answered by Shaykh Amjad Rasheed
Does smoking break one’s fast?
Our leading imams say that smoking does break one’s fast and it is haram to smoke during the day in Ramadan, like any other obligatory fast. This is because smoking has a substance that appears in the body of the cigarette, and it is a fact that a fast is invalidated by any substance reaching the body cavity, if the person does so intentionally and knowing that it is haram.
Imam al-Bajuri said in his Hashiyah `ala sharh Ibn Qasim (1:302), “And one of the substances [s. that invalidate the fast] is the well-known cigarette-smoking . This invalidates the person’s fast, because it leaves a trace that is tangible, as it is seen inside the cigarette.”
And al-Shibramillisi related in Hashiyat `ala Nihayah from his Shaykh, al-Zayyadi, that he used to give the fatwa that smoking didn’t break the fast, then some of his students showed him the remains from smoking in the pipe, so he took his first fatwa back and maintained that it does break the fast because it has a substance.
Amjad Rasheed
[Translated by Sr. Shazia Ahmad]
Faraz notes: The Health Consequences of Smoking: A Report of the Surgeon General
http://www.surgeongeneral.gov/library/smokingconsequences/