All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The scholars differed in opinion in regard to a fasting person who inhales incense whether or not his fast is invalidated. There are two opinions in this regard. It might be the most correct opinion that inhaling incense does not break the fast because it is neither food nor drink nor something similar to it. This is the view of the Shaafi’i School of jurisprudence and this is the opinion chosen by Ibn Taymiyyah . Nevertheless, a fasting person should avoid inhaling it as we clarified in Fatwa 83507.
Even according to the view that it invalidates the fast, smelling the smell of smoke whether it is from incense or cigarettes, does not break the fast; rather, what breaks the fast (according to this view) is inhaling it and not only smelling it. Ibn ‘Uthaymeen said: “I hear too much about people asking about incense for a fasting person and they believe that smoke breaks the fast, and this is not correct, because it does not break his fast unless he inhales it and it enters his stomach.” He also said: “…because smoke does not enter the nasopharynx unless one inhales it.” Furthermore, it was attributed to him that he does not use incense during the day of Ramadan and he denied this saying: “I call upon this brother to convey the truth, because he lied about me whether he did so deliberately or not deliberately. I did not say ‘do not use incense’, I use incense while I am fasting and there is nothing wrong with this. What we mentioned is that one should not inhale incense, i.e. he should not put the incense next to his nose and inhale it, because if he does so, the smoke will enter his stomach.”
Even if we presume that one inhales it, his fasting is not invalidated unless he deliberately inhales it. However, if he smells it and it enters his nose without doing so deliberately, his fasting does not become void.
If someone does one of the things that invalidate fasting out of ignorance or out of forgetfulness, then his fasting does not become void.
To sum up, a person who smells smoke of incense or cigarettes or scented candles is not obliged to make up his fast, and the same thing applies to the one who inhales it by mistake.
Allaah Knows best.