Ask Hackaday: Open Fire Suppression and Safety Standards

We posted about a 3D printer fire a while back. An attendee of the Midwest RepRap Fest had left his printer alone only to find its immolated remains on his return. In the spirit of open source, naturally, he shared his experience with the rest of us. It occurred to me that hackers are never powerless and there are active things to be done and avenues to explore.

An animation of a commercial fires suppression system, fire trace's, operation.
An animation of a commercial fires suppression system, fire trace’s, operation. Firetrace‘s website has more.

There are really fantastic commercial fire extinguishing systems out there. One implementation, which is commonly deployed in cabinets and machining centers, is a plastic tube pressurized with an extinguishing agent by a connected tank. When a fire breaks out the tube melts at the hottest locations, automatically spraying the area with a suppressant. Variations of this involve a metal nozzle filled with a wax or plastic blended to melt at a certain temperature, much like the overhead fire sprinklers.

This system is also used inside engine compartments with success. For example, this item on amazon, is nothing but a pressurized plastic tube with a gauge on one end. Since the inside of an engine compartment can be treated as an enclosed space, very little fire suppressant is needed to extinguish an unexpected flame. It is important to note that this system works in a high temperature environment like an engine compartment, which bodes well for enclosed build envelopes on 3D printers.

BlazeCut Automatic Fire Suppression System 6' TV200FA, Automotive Extinguisher
BlazeCut Automatic Fire Suppression System 6′ TV200FA, Automotive Extinguisher Installed under Car Hood.

Another option is to construct a suppressant mine. A Japanese and a Thai company have both come out with a throwable fire extinguisher. In the Japanese device, the outside of the extinguisher is a breakable glass vial which shatters upon impact; releasing the agent. The Thai device looks like a volley ball, and releases the agent upon the application of heat. This device seems like a better candidate for 3D printing or home projects. Imagine a small rectangular pack with adhesive on one side that sits near the possible fire points of the printer, such as under the bed or above the nozzle. In the event of a fire, the casing will melt and the system will automatically deploy a spray of extinguishing agent.

Most of the chemicals used in these constructions are benign and readily available. High pressure tubing and waxes can all be purchased and the desired melt points can be aligned with their datasheets by need. Plastic sheets are not hard to procure. These offer a nice solution due to their entirely passive nature. They don’t need power to operate and rely entirely on the properties of the materials they are constructed out of.

There are other options in active systems. Hackaday readers suggested things such as flame sensors for adding automatic cut-offs in case of a fire. Thermal fuses can also be considered in some cases. There are other tricks too, which are less kosher but will work nonetheless. For example, placing a critical wire, fuse, or component in the likely path of a fire so that it is destroyed first, stopping the operation of the device quickly. These avenues should be explored. At minimum there should be at least one project that uses a Raspberry Pi and an Arduino to tweet that fire suppression failed and the house is on fire.

The Thai invention is a volleyball that melts upon contact with flame and releases a pressurized extinguishing agent.

Some of the big questions to ask are on the legal and ethical side. If someone started selling kits for a DIY fire suppression system and a fire ends up destroying someone’s property despite the device, who is responsible? Is it even safe to post instructions? What if a kit prematurely sets off and injures someone. I imagine a big part of the cost of these professional systems is some sort of liability insurance and certification. Still, putting a six hundred dollar fire suppression system on a six hundred dollar printer seems silly, and something is better than nothing.

Lastly, the comments directed a ton of flak towards the certification systems. There should be no reason that open source projects can’t produce their own specification for safety. An open source specification without an agency naturally couldn’t provide a legal defense against property damage, but a thought-out test program would provide piece of mind. For example, in the case of 3D printers, one could have a set of basic fail-safe tests. One example would be bringing the printer up to temperature and rapidly disconnecting the thermistor, does the printer erupt into fire? No? Good, it meets the spec. I wouldn’t mind knowing that the latest version of Marlin was tested on the popular boards and still met the community specification for fire safety.

As far as I can tell, there’s been very little work in open sourcing safety systems or in providing a testing framework for ensuring open hardware meets basic safety conditions. Many of you have experience with these systems. Some of you have gone through the entirely un-enjoyable process of getting a UL certification. What does Hackaday think?

73 thoughts on “Ask Hackaday: Open Fire Suppression and Safety Standards

  1. Enclosed 3d printer with a vacuum pump removing the air surrounding the print.
    No O2, no Fire.

    Bonus under a strong enough vacuum you don’t need to worry about moisture in your filament, There will be no cold drafts to warp your ABS prints, hot end and bed will heat up faster with out the air pulling drawing away the heat.

      1. Is that correct? I thought warping was caused by the printed part shrinking as it cooled. If it didn’t cool down till the end, it would cool uniformly.

        Isn’t that why some printers have heated chambers?

          1. I think a better use for a CO2 cartridge in this context would be for fire suppression. If you popped one when smoke was detected, it should be able to extinguish anything inside the printer cabinet.

      1. Doesn’t the enclosed space, only need to be air tight? If there is a flame, it would quickly consume the oxygen in the enclosed space, and go out. That doesn’t solve the run away heater problem though. Maybe a smoke detector on the inside too.

  2. I have been using a pid controller to make yogurt. which is a half day process which I am not about to sit and watch. so the simple steps I have taken to minimize fire risk are at the forefront of my design thinking.

    1. ceramic tiles for thermal/flame containment.
    2. wire size matches or exceeds rating for circuit breaker. heating element maxes at ten amps, who cares it is on a twenty amp breaker so i use 12 gauge wire.
    3. ul listed heating elements in their listed enclosure with all factory safety devices left functional.
    4. all wiring meets or exceeds nec. all enclosures grounded or double insulated.
    5. smoke alarms tested monthly. fire extinguishers placed conveniently to doors/walkways.
    6. think about safety for every design.
    7 be paranoid if you are going to leave it unattended.

    Next version propane burner. more safety devices to come.

  3. A six hundred dollar fire suppression system to protect a six hundred dollar printer is indeed a little silly. A six hundred dollar fire suppression system to protect a 100,000+ dollar house, not so much.

  4. Perhaps flooding the cabinet with nitrogen while printing, to prevent fire in the first place?
    I am not familiar with the filament but I do not think it requires an oxygen atmosphere to work.

    Nitrogen canisters are pretty cheap at the gas shop, and it wouldn’t take a very high rate of flow to keep the oxygen level inside the printer low.

    1. I wonder if there will be some unexpected improvement in the fusing of materials / general behavior of filament when hot when using nitrogen. There might be some synergy here…

    2. Or use a nitrogen generator (that separates N2 from the mix of gasses in the air). Commercial ones are regrettably priced… has anyone hacked together a (cheap) homebrew N generator?

      N2 could flow forever!

      1. Surplus O2 concentrators turned around (ie, plumb the exhaust instead of the official outlet) can deliver a few L/min. Those used by people severe breathing ailments have been used by other hackers (notably Ben Krasnow on his AppliedScience youtube channel) to build LN2 generators, so they can’t be prohibitively expensive.

          1. There is only going to be a ‘high oxygen environment’ in the area immediately surrounding the exhaust port. That won’t exist very long due to natural air mixing and HVAC present in most rooms.
            Add in that if the concentrator is able to deliver 1-10 L/min of +90% O2 thats 4-40 L/min of N2, so there’s little need to run the machine at full power.
            Any number of simple methods could be used to increase the mixing rate and remove the threat of the oily rag on the same bench bursting into flame.

  5. EE here that has been doing industrial controls hardware and software for the past 7 years.

    Fire suppression is a silly way to handle this, you needs to make sure the design is such that a fire simply cannot happen with a single point failure (heat rod falls out). That is UL 101.

    On top of that software should monitor voltage and current (power) in and temp delta and if the two do not match shut it down and throw an error.

    1. I completely agree. Rate the components better, use high quality connectors, properly rated wires, multiple fail-safes.
      And for the love of god stop putting 15 amps through a 12v power supply. Higher current = higher fire risk. It’s Ohms law, basic math, and completely unnecessary!
      Firmware failsafe, hardware failsafe, properly rated components, fireproof components. do that and it won’t catch fire. you worry so much about putting out a fire, how about stopping the fire from happening in the first place.

      1. Correct components (overpriced, but safer) will solve a part of the problem. But after all that kind of efforts, or in case it’s impossible to build or scale your own hardware (when relying on COTS), why not add a simple Fire Suppression?
        Fire Safety is something WE ALL should think about. Not only those developing a product, also the people who install or own a product, or it’s main users.
        And one should never depend a single safety mechanism (No manner how safe your device is advertised. It won’t gain my trust).

        I’ve been investigating this topic for a while, and it’s quite interesting to see what kind of products are available on the commercial market. FSD, StatX and many others develop Aerosol suppression systems. And those volleyballs are also sold in the form of (for example) FireKnockOut.
        The latter is something I might actually buy and place it close to my NAS and router (or close to flammable liquids, which I’d store in steel fireproofed cabinets). Not to prevent the initial fire (that’s another step in the process).

        Build non-flammable safeguards around (self-build, or maybe all) electronics, from aerated concrete (or even drywall/gypsum) for example. And test if it holds/contains the fire for 4 hours (paranoid, standard test is 1 hr?), and/or out-of-fuel.

        I’d like to depend on a mix of DIY and commercial solutions, in the hope that one of the suppressors would extinguish / contain it. Just in case someone else made a @#$%#$%.

        I’m highly tempting to build an early suppression system with a modified (electrified) CO2 extinguisher. Which cools down my NAS / router-fire, and replaces all oxygen (don’t forget proper vents). Before the “expensive” (relative) solution (FireKnockOut) would be activated, which would be located ~1 meter above the fire-hazard.

        It’s really the combination of factors. That’s why I like the “Open Safety Standards” part of this post.

      2. While I agree with you both that everything should be designed and built to minimize the risk of fire, in reality the materials, construction, and use of the equipment will at some point lead to a non-ideal circumstance which poses a fire risk. What happens when the electrolyte in the caps in the feedback circuitry goes dry and the controller starts getting incorrect inputs? Design for perfection – plan for disaster.

        1. Absolutely. All systems eventually fail. Period.

          It’s silly to to say the way to prevent fires is just to not catch fire in the first place. If that were the case, why do sprinkler systems exist at all? 3D printers move a lot. Eventually the wires will fatigue. It might be a long time, some other component might fail first. But SOMETHING on that printer is going to give up the ghost.

          Any time there’s a source of energy you need fire suppression. I’ve built 60 megawatt switchgear in a completely enclosed block structure with ZERO flammable components and sprinkler systems still went in, and with good reason. And yes believe it or not, industry standard practice is to spray water on failing 27.6kv switchgear. That’s a topic for a different day…

          I’ve put a few FM200 systems in smaller building for generators and stuff. They’re pretty decent actually. If I were going do something like this, that’s the way I would go. They’re really easy to interface to as well. They’re usually sold with some locked down piece of crap panel from Simplex Grinnell or whatever, which are terrible and I hate them. It’s a very simple solenoid (12v DC maybe? I dunno) trigger on these systems. It would be trivial to design an open system to deploy FM200.

          1. > spray water on failing 27.6kv switchgear
            Mother nature is a big resistor! Neat practices.

            FM200 is funny indeed! But those systems just cost too much for the average home-owner. Too expensive to protect the average modem + NAS corner. Esp. when I compare it with the price of a CO2 extinguisher.
            For a experienced DIYer it might be possible to build such system. The hard part might be getting FM200 in a proper storage (with electric valve?).
            I’d like CO2 because I’m capable of doing refills at home. Just fill the extinguisher for ~40% (or something? please lookup!) with dry-ice pallets and wait a few days for the system to pressurize.

            It’s also possible to “modify” Aerosol Extinguishers (non-refillable, spray-paint canister like) by adding a spring-loaded + electromagnet released mechanism.

            The average DIYer should not try to contain gaseous substances. I’d try to outsource that part (to be sure it isn’t empty when needed).

      3. lower current doesn’t necessarily mean lower risk if components and conductors aren’t sized to handle the current to produce the needed power. You began on the right trackis describing part of the problem., but got off track when you got sidetracked bashing 12 V. Many motor vehicles operate for hours on end with higher current need to produced the required power with a nominal 12 V supply. Electrical fires in motor vehicles don’t appear to occurring in alarming number.

        1. the difference is that motor vehicles have relatively stationary wire, at gauges from 00 to 8 or so. Those gauge wires are expensive, and completely useless in a 3d printer. Once you start bending the wire and putting them in enclosed spaces of 100C or so, things get tricky. Don’t forget that the traces on the PCB’s need to handle the current too, do you know how wide a 1oz/ft trace needs to be to handle 15 amps? What about wire insulation? PVC will harden and fail over time when subject to too much hear (or too much time). 3d printers use mosfets for load switching, while cars use relays that can handle much higher loads without concern for thermal runaway or heatsinking.
          Efficiency is another problem too. the stepper motors will be more efficient when driven with higher voltages. losses in wires and connectors will be less. It’s positively ignorant to believe that a 12v system is the optimal choice for use in a 3d printer.
          There is a right application of 12v power supplies, and a wrong one. Even still, cars could undoubtedly benefit from a higher voltage system, but that is another topic for another time.

      4. It doesn’t matter if you build it properly and do it properly, people will just say “I can do it myself with a $10 power supply from AliExpress” and go and ignore your good quality engineering anyway.

  6. Should a 3D printer ever get anywhere near hot enough to burn ? Assuming not, then a thermal cutout for prevention would seem a much more appropriate approach than curing with an extinguisher.

    1. What happened with the printer in the photo above is he had just taken apart the hot end to clean all the crap that eventually builds up on it. When he put it back together he either didn’t get the grub screw tight or forgot it all together. When the print started it was working fine, he left for a couple hours, and that’s when the heater cartridge fell out of the hot end. When that happened the printer saw the drop in temp and told it to get hotter, which it did, problem was it was laying on the print bed now. Printer didn’t see a rise in temp so it kept raising the temp until either the bed caught fire, or the cartridge caught fire. Either way, the printer should have shut down when it saw it wasn’t changing temperature the way it was supposed to. I was talking to the guy when someone else mentioned their printer failed to shut down for something similar, their thermistor wires broke, and caused a runaway heat up.

      1. I have this printer and the manufacturer claims it would not have happened had the firmware been updated. Supposedly they added a timeout so that if it doesn’t reach temperature within a reasonable amount of time for any reason it will just shut down.

  7. The core question in the end of this article is right. Who is liable?

    Really i would not comment how to design a safety system until the liability question is answered. As we have seen through the courts, Good guys (ie people giving advice) are liable for Bad Advice leading to personal harm.

    I would love to help, but the @$$^@% lawyers make doing so a personal risk…. isn’t that sad.

  8. IMHO, this article and the comments above bring up some very good points regarding designing for safety. This is a concern well beyond the specific application discussed here (3d printers) – almost anything with a heating element or volatile chemicals or high current or any variation of lithium batteries is a potential fire risk. So domain knowledge of both the design side and the suppression side would be immensely valuable to share with the community. And yes, even if there is not an official community standard, it would be very useful to have some hacker-friendly guides to safety considerations.

    Case in point. [Stephanie] mentioned that high current increases fire risk. If so, then maybe using a higher voltage/lower current supply would be a smart safety tradeoff. But doesn’t the increase in voltage also increase safety risks from arcing, wayward fingers, and other factors? Is the tradeoff all that useful if the device is still heating up to 100*C or more? Those of us who have not taken coursework in these areas can guess at some of these details, but even a wiki with general guidance would be a welcome resource.

    1. typically 36-50v would be the limit of safety. Even just moving to 24v would be a huge improvement in safety. The current would be halved, with no significant rise in arc hazard. Many designers are already starting to move to 24v, but it has not reached mass adoption. Cost savings can be significant, as you can have thinner wires and cheaper connectors and still have less risk.
      The ONLY reason 12v is the standard is because PC Power supplies were the original power source (and are still used in abundance).
      The heaters themselves are not an issue, the failure points are more commonly bad connectors, poorly rated wires, and overheated electronics cause by large current draw.
      The heaters require thermal fuses, firmware safety features, and secure mounting. Along with that the wires need to be properly insulated, and any flammable materials should be replaced. There is a reason I can hold my 450 C soldering iron in my hand without it bursting into flames.

      1. Yep, and if the heater has a PTC element in it, it can’t start a fire because it’s self-limiting.

        I believe there’s heating wires made specifically for certain temperatures, so that you can cut any length and it will only heat up to 50 C at 110 Volts. Design one that goes up to 200 C and no more, and you’re set.

        1. Unfortunately the most popular heating elements have no inbuilt limiting.

          The real problem is that there is no fail safe engineering on these machines. The hot end should be designed so that the heater cannot fall out and still be active, the thermistor and heater control loops should have a non-software initiated shutdown if the loop goes open, and all the wiring and connectors should be spec’d and routed so that normal operating stress doesn’t cause a short or overheat from a bad contact.

  9. Having worked for years as a fire suppression specialist I read the article with interest.

    Liability is a serious issue but is also limited.
    In the end the functionality of a system remains the responsibility of the owner.

    He is also responsible of the selection and sizing of the installation. If a system is failing to suppres a fire due malfunctioning or a bad design the only person to blame is the person who took the decision to install that specific installation.

    This is why most installations are largely oversized and professional companies will evaluate each request to review wether their system offered is suitable for the risk to be protected.
    I have had several cases where we decided not to follow the strive of the customer to pay less.

    Fire detection is an art and science.
    Fire suppression is brute force.

    Some advices:
    Try to detect as early as possible a potential issue and build in a staggered reaction system.
    Don’t create more dangerous situations than necessary (gas flooding systems can be lethal)
    Try to be as complete as possible when evaluating risks and spend some extra money to use professional solutions that have functionality and safety related approvals for critical parts that might be the source of dangerous situations. Thermostats are a known source of fire.
    Invest time in reviewing you own designs.
    Learn to use build in safety mechanisms: there is a reason almost all microcontrollers have watchdog systems/timers.
    Make sure controller system sensors can not stop sensing what they require to sense and build in detection systems that capture defect sensors.

    1. Thanks for these advices !
      I totally agree with the lethal aspect of gas flooding systems: I work in a datacenter and we are not very confident when working in an area “protected” with this system.
      I heard about a water mist system that was said to be (surprisingly) safe for hardware (computers). A famous french Internet Provider uses it:

      I suggested my boss to own a funnier system:

      … but he disagree :)

      1. Some gaseous systems are safe, others are not. Halon and its successors are effective at small concentrations. Now, you don’t want to hang out in the area, but you should be evac’ing anyway and have plenty of time to do so.

        Systems that try to remove oxygen (argon etc) however can certainly cause asphyxiation.

      2. Holy shit! I’d not want to be in that place when the suppression goes off! You’d drown in the foam! We had a system false positive on a reflection(we think) of the sun off a aircraft tow tug. All the fire cannons fired, one right down the intake of a jet engine. In 5 minutes the hanger was about 6 feet deep in foam. We couldn’t open the doors though, it was in the negative 40’s that day.

  10. Sometimes I wonder if just a plexiglass box and a big water balloon suspended above it would be the easiest. Add GFCI and a catch basin around it (the box isn’t necessarily water tight) and we should see the system kill itself with little issue.

    Of course, the first line of defense is the temperature control loop shutting down if there’s a thermal runaway. Industrially, I’d also have wired two relays in series with a “high current” output just to guarantee it gets killed, with a manual re-latch.

  11. When I moved into my new apartment a few months ago, the range hood had two “range queen” units and I was responsible for a whole lot if I removed them. They are relatively small, about the size of a can of sterno, attach to the hood with a metal split ring and have what looks like a spring loaded valve held closed by something meltable. tells me they are about $60 and are filled with pressurized powder. Add this to some device to shut off the electricity in the event of too much heat or flame, and you’ve got something that should hang over any high heat, high current unattended device.

    1. I was going to suggest these as an idea as well. There is a reason that restaurant systems are so “simple”. Mechanical linkages held in tension by a solder pot, it’s stable and can sit over harsh environments for years with very little degradation of service. Think of the simplicity of a sprinkler head and the very low failure rate. Only very specific and socialized systems (like the aircraft hanger system) should actually rely on anything electrical to set them off.

  12. NFPA standards are all free to download with a free registration:
    They outline all of the system requirements for different installations, though I don’t think I would install a system myself.

    There are a few different standalone fire suppression systems like firepro:
    These can be installed with little to no extra equipment and will protect your house and other equipment.

    DIY and opensource is great for alot of things but when your financial future and potentially your life is at risk you should leave it to the folks that know what they are doing.

    1. I’m fairly certain that the NFPA is an arm of the insurance industry. The insurance industry has a financial interest in promoting reasonable fact and research based requirement.. Unnecessarily strict requirements means their guidelines will not be adopted, and can’t sell their product: too lax they will go broke because of unnecessary payouts. I sure no one uses the civil courts more than the insurance industry, so why would anyone do anything other than follow their guideline and requirements? Being bull headed and going your own way will, as Grazz pointed out cost you dearly if going your own way results in a loss for someone else.

      1. Nobody exiges you to follow these guidelines, except an “authorothy having jurisdiction”
        Now this is a very tricky denomination and in the end with respect to your property the first authorothy having jurisdiction they will encounter is YOU.

        The NFPA is a well written evolving encyclopedia of safety guidelines the will cost you some time to work out your set of rules. But it will also help you to stay out of certain danger zones that might force you to inform the goverment and have the fire chief come over to inspect what the heck you are doing.

        With respect to safety laws are in place, and require to be obeyed. If you are sure they are wrong, first go to high court to get them altered/removed before doing differently.

  13. Some non-obvious facts of 3d printing: filament eventually tangles up and if it is not free to unwind in two axis it will risk snapping, a cartridge will continue even without filament causing overheating of filament, which is no more pushed.
    Thermoplastics are often flammable at higher temperatures.
    Hair spray is highly flammable, if you use it as hot bed fixer take care to ventilate the chamber after spraying. Never spray it near hot soldering iron.
    A heated chamber or fume extractor will mask the burning smell of filament, which is easy to spot. PLA burns at 400°C and start smelling at 260°, so if you can feel the smell you can prevent fire.
    Filament leaking between the screw and the hot end is a fire hazard.
    Hot end insulation is safer made from ceramics or kapton. Kapton glue may catch fire at 300°C, but only if exposed to air. Kapton glue will evaporate over time.
    Hexagonal and octagram infill cause LOTS of vibrations at high speed and high infill. This stress can cause the thermistor to slip off, thermal paste to detach, solder joints to break and non-rubber blocked screws to loosen.
    Crimp or screw connectors are more resistant to vibrations than solder.
    Keep out or warn smokers and children about dangers.

  14. Push-fit nylon hose is cheap and plentiful, add a few joiners, thread an adapter onto a CO2 or similar extinguisher (or just a container of water/extinguishing media above the assembly) and trail round above whatever might catch fire.

    Also: You can get smoke/fire alarms that are immune to the fumes given off, designed for kitchens, bathrooms, etc. to ignore burnt toast, steam, etc.

  15. Fire triangle: O2, combustible, heat.
    What if move the printer inside an old refrigerator or freezer?
    It will keep only a limited quantity of O2 inside, while keeping constant temperature.
    It will keep all the fumes inside (that’s good or bad) and also it will keep all cool or even cold.
    Add a thermal camera and if it detects temperatures above burning point of the most flamable material from the printer, it should cut the power to the printer and refrigerator.

  16. It would be better to not have a supression system at all. Just haVe an enclosed build volume, and fill it with nitrogen gas every print. Then it cant burn. Also, change the code controlling the heating element so that a fire can’t happen. If no temp increase occurs with power on the heater, turn off the printer and display an error. Simple enough.

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