All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Using perfumes, attars and scented soaps while fasting is permissible and bad smells do not affect the fast. Smells, whether good or bad, do not usually have sufficient substance to enter the stomach. However, the Muslim scholars have different opinions regarding incense. Some scholars are of the view that it is disliked to use it during the fast while others believe that inhaling it breaks the fast since its material parts reach the stomach.
Nonetheless, the correct opinion is that smelling incense does not break the fast even though one should refrain from using it in order to avoid any doubts.
Allah knows best.