Incense-burner in front of people who are praying

There is nothing wrong
with that, and that does not come under what some fuqaha’ have mentioned
about it being makrooh to pray facing fire. For those who say that it is
makrooh to pray facing fire give the reason that that is akin to the actions
of the Magians (Zoroastrians) who worship fire, but the Magians do not
worship fire in this manner, so there is nothing wrong with putting the
incense burner in front of a person who is praying. There is also nothing
wrong with putting electrical heaters in front of a person who is praying,
especially if that object is put in front of the members of the congregation
only and not in front of the imaam.