We would like to draw your attention to the following verdicts of the maraje’:
It is an obligatory precaution not to allow the smoke of cigarettes and tobacco and the like to reach the throat while fasting.
Ayatullah Khamenei: As an obligatory precaution, smoking isn't permissible while fasting.
Ayatullah Makarem Shirazi: It is an obligatory precaution that one who is fasting abstains from smoking cigarettes and all tobacco products and also not to allow thick smoke reach his throat, but going to the shower where there is steam is okay.
Ayatullah Bahjat: The fast not being broken by dust and smoke that isn't thick and isn't a substitute for food or isn't tonic, isn't devoid of reason, although abstaining is ahwat (in accordance with precaution).
Ayatullah Nouri: The fasting individual must abstain from thick steam that changes back to liquid in the mouth and also, as per obligatory precaution, must not allow the smoke of cigarettes and tobacco products and the like to reach his throat.
Ayatullah Zanjani: In the holy month of Ramadan, smoking and using tobacco products openly in a way that is disrespectful to the fast is impermissible, and if it isn't disrespectful, it is still impermissible as per precaution, and in the case of an individual smoking, he should still abstain from all other invalidators of the fast till iftar, and also must perform the qaza (make up for) that day.