A simple smoke machine using dry ice (won't set off smoke alarms) and a remote controller.
The cannister is made with PVC, and using a homemade pressure bag, with a check valve in place to prevent back pressure from the dry ice. On and off with a remote switch and an aquarium pump. We have used it for airway fire scenario and an OR fire scenario. Total cost $45 +/-

Patient Safety Training Center
Dartmouth Hitchcock Medical Center