3D printers use high temperatures to melt and fuse plastic. There is the same danger that is involved in any other high temperature appliance.
Here are some common sense precautions to take in case something should go wrong with your machine.
1. Do not leave the printer unattended. Our advice is to treat a 3D printer as you would an oven. There is no need to be watching it every instant, however you also should not leave your house while it is running.
2. Have a smoke detector in the same room as the printer. Test your smoke detector regularly and make sure the batteries are good.
3. Have a fire extinguisher. Keep the extinguisher in a place where you will have easy access to it in an emergency. An ignited 3D printer will be an electrical fire, so make sure you have a Class C extinguisher. Also make sure your fire extinguisher is not expired.
2. Keep the printer away from anything flammable. One case of major injury due to a 3D printer was caused by it being operated near pyrotechnics.