Summonig

Yes you can, although I personally think that burning good-quality incense is a sign of respect for the Demon/ess that you are summoning.If you cannot burn incense or candles indoors (as it is the case with many apartment buildings because of the fire detector in each unit) then not using incense for a summoning is possible.
Hail Satan.

  Can i summon a demon without burning incense?