Fablabs mainly use 3D printers with filament; these can catch fire, for example if the heating of the nozzle is on and the control loop to switch it off is disturbed. So always keep a human eye on things, possibly from a distance, but at most from the adjacent room, for example via a RaspberryPi with camera and Octoprint.
Powder-based 3D printers do not use heat during the actual printing; in principle they could work unattended. For example, the Z 850 is (was) a large, closed machine with a relatively large print volume that can print for days on end without human intervention. If desired, the machine will send an email when a print job is almost complete. Such machines do require quite a bit of attention in terms of ventilation, not because of fire hazard, but for health reasons. They are relatively expensive and are mainly used by larger institutes where the costs for some extra sensors are not a problem and there are always night watchmen nearby.
Does this help you?