If you've been active in the online 3D printing forums, it won't take long to come across a picture of someone's printer after a fire. But does that mean your new cool toy is going to kill you in your sleep?
Part of the problem is the sheer of printers out there. Say, for the sake of argument, there are 10,000,000 3D printers out there. All it takes is for .0001% of these to catch fire, and there would be 10 people posting pictures on Reddit.
There simply aren't hard numbers on how many printers catch on fire, and how many of those events do any real damage. But a fair comparison is an oven: it also gets scorching hot and is in everyone's kitchen. Most of the time, the stove is perfectly safe, but it is not unheard of for one to catch on fire, especially if left unattended.
It's rare but does happen, which is why every single 3D printer manufacturer gives explicit instructions to never leave a 3D printer working unattended.
Which begs the question of what can you do about it? No fire mitigation strategy is 100%, but there are varying levels of protection you can look at.
No Brainer Protection: Smoke Detector/Fire Extinguisher
The first level of protection is obvious: buy an extra smoke detector and place it directly above the printer, and put an extra fire extinguisher in the room where it's convenient to be snatched in an emergency. Before anyone comments that this is super obvious, how many 3D printer owners buy an additional detector and put it over the printer? I like the Wifi enabled smoke detectors as they will alert your smartphone when there's a problem. Mostly it lets me know when my kids are burning popcorn in the kitchen, but should the worst happen, I'd be the first to know. Nest has a nice feature that gangs all of the detectors together, but that's the only brand I'm familiar with.
Intermediate Protection: Smoke Cutoff Power Supply
In my experience, the only way a 3D printer catches on fire is through an electrical problem: frayed wires, a broken connector, or a DIY mod gone wrong.
As an electrical engineer, I was excited to start designing a product that would cut off power to a 3D printer when it detected smoke, theoretically stopping a fire before it got out of hand. The design was almost finished, but then this cool device showed called the SmartMicro™ showed up all tested and UL approved and ready to go, so it was a no-brainer to go with it instead.
The idea is simple: plug in your printer and then position the detector inside an enclosure. Keep in mind it is only designed to work inside an enclosure with concentrated smoke.
Pro: Automated Fire Extinguisher
The BlazeCut™ automatic fire suppression system is perfect for 3D printers, designed to work in enclosed spaces with electrical fires. It works by spewing out liquified gas, the HFC-227ea fire extinguishing agent. According to the manufacturer, it is a "worldwide known and accepted gaseous clean agent used for total flooding fire suppression applications with very high effectivity, zero ozone depletion potential, and safe to people. "
The tube has a temperature trigger on one end that reacts when the temperature gets over 105C. Fire retardant would be exploded all over the inside of the enclosure, covering the printer and smothering any fire. Here's a demonstration from BlazeCut using the Lack enclosure:
Which level is the best for your situation?
Certainly, everyone should buy a separate smoke detector and place it right above the 3D printer. And buy a fire extinguisher and place it right next to the printer.
But the choice between a smoke cut off power supply and an automatic fire extinguisher is tough; ideally, they compliment each other. Say the fire extinguisher exploded and the power supply was still on. Theoretically, something bad could happen, such as exposure power cable wires waiting to fry someone. Anecdotally most 3D printer owners don't do any fire detection or suppression, so any of these measures will reduce the risk to you and your family.