3D printers have a small fire risk.

The model I post here is a simple holder for a BW24 extinguishing cookie from brandwaechter24.de I have dangling above my 3D printer. The cookies are sold for E 20 each and are supposed to burst open and release 0.5 kg extinguishing powder when hit by flames. They have a nice video on their site demonstrating. On their site they posted a holder model for screw mounting, but I needed a hanging one, so I designed one.

I use it in combination with a smoke detector that I use to switch off my printer when it signals. In another post I will put the model for the little box I made to put the relais electronics in. And I have a small fire extinguisher hanging nearby, else a smoke detector makes no sense, you have got to be able to do something. I haven't been able to test the cookie, but above measures gives me a better feeling of safety.

Next to this I try to print always while being in the house, I use an old phone as remote camera, I have runaway protection enabled in my printer software, and use an auto-off bracket so my Ender automatically switches off the printer after the job.

But more important is to have a decent check of the electrical hardware of your printer on esp. the high current circuitry connected to the print bed and nozzle heater. Are wires thick enough, sufficient bending radius, strain relief? (you find some brackets on Thingiverse) Have original connectors been used? (clones are dangerous!) Are fuses in place? Is the thermistor well fixed (still?)? Decent power supply manufacturer? Motherboard in a metal enclosure?

This little cookie and its holder can be your last layer of protection in case of fire!