Here’s a part of a cabinet in my wardrobe where my printer lives. It’s a bit noisy with all those hard surfaces so I am just about to put up some foam padding on all 5 sides.
Is that stupidly dangerous?
You can see I have a smoke alarm there, but it won’t stop a fire on its own.
Edit: the cabinet has no door, it’s always open like in the photo, but the wardrobe door is generally closed. The room has some ventilation so smells do go away.
Id say you are fine, but I would add a fire extinguisher like others suggested, just in case. Many people have cheaper printers in ikea lack enclosure, which is made of cardboard, but they are not good example. Proper solution would be a metal enclosure and you being there while printer is on. But come on, who got time to watch printer for 20h or so.
If noise is too high in next room, you can reinforce your cabinet with some metal brackets or stop vibrations with rubber or simmilar. You need to find where noise is comming from. Also, you can add acrylic door (with holes on top/bottom for airflow), it should reduce noise significantly. Put thermometer inside and check temps after long prints. If enclosure gets too hot add more holes or a fan.
If you put insulation inside the cabinet, use some screws to make sure it doesnt fall off from the heat
Printer on a concrete or stone slab decoupled with thick rubber. Make sure the cabinet can handle the weight as you are adding roughly 30-40kg on a 25x25cm area.