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, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Smoke does not invalidate fasting if one unintentionally lets it reach his throat. In his book Kashshaaf Al-Qinaa‘, the Hanbali scholar Al-Buhooti says:
A person’s fasting is not broken if a fly, dust, or flour dust reaches his throat without him intending so. This is because the person did not intend it, just as when he is asleep. This implies that whoever intentionally swallows smoke shall have his fasting invalidated.
In the Hanafi book Radd Al-Muhtaar, the author said:
"(A person’s fast remains valid) if dust, a fly, or smoke enters through the person’s throat, even if he was conscious of the action because it is not possible for him to avoid such things. This implies that one's fast is invalidated if he intentionally allows smoke to enter through his throat."
In the Encyclopedia of Fiqh, it says, “If dust, a fly, or smoke enters through his (the fasting person’s) throat without the person intending so, and even if the person is conscious of it, then the person’s fast is unanimously judged to remain valid, as stated by Ibn Juzayy.”
The smell of basil has no effect on the validity of fasting. It is only disliked to smell it while fasting, as stated by some Muslim scholars, such as the Maliki scholars.
Allaah Knows best.