Hack Safely: Fire Safety In The Home Shop

Within the past two months we’ve covered two separate incidents of 3D printing-related fires. One was caused by an ill-advised attempt to smooth a print with acetone heated over an open flame, while the other was investigated by fire officials and found to have been caused by overuse of hairspray to stick prints to the printer bed. The former was potentially lethal but ended with no more than a good scare and a winning clip for “Hacking’s Funniest Home Videos”; the latter tragically claimed the life of a 17-year old lad with a lot of promise.

In light of these incidents, we here at Hackaday thought it would be a good idea to review some of the basics of fire safety as they relate to the home shop. Nowhere was this need made clearer than in the comments section on the post covering the fatal fire. There was fierce debate about the cause of the fire and the potential negative effect it might have on the 3D-printing community, with comments ranging from measured and thoughtful to appallingly callous. But it was a comment by a user named [Scuffles] that sealed the deal:

“My moment of reflection is that it’s well past time I invest in a fire extinguisher for my workstation. Cause right now my fire plan pretty much consists of shouting obscenities at the blaze and hoping it goes out on its own.”

Let’s try to come up with a better plan for [Scuffles] and for everyone else. We’ll cover the basics: avoidance, detection, control, and escape.


The hacking lifestyle is full of “do not try this at home” moments. We routinely play with high voltages, open flame, high temperatures for soldering and welding, volatile and flammable solutions — and sometimes all at once. When you’re in the zone on a build, you may not notice the stray datasheet that fell across your soldering station, or the fact that you’ve plugged one too many instruments into that power strip. All it takes is a second for a situation to go very bad.

Case in point: back in grad school, I showed up late one night to the lab to tend an experiment. As soon as I unlocked the door I knew there was trouble; the scent of burning plastic hung heavy in the air. I investigated further and found a smoking puddle of molten packing foam lying around a Bunsen burner on one of the benches. Apparently a fan had started automatically and dislodged the foam from a shelf; it wafted down and landed perfectly on the burner which had been left on by our technician at the end of the work day.

It was the perfect storm of factors, and only by chance was I there to intervene and prevent the fire from spreading, but it illustrates a few important points:

  1. You need to do a safety audit of your workspace on a regular basis. Make sure nothing can conceivably cause fuel to be exposed to heat in the presence of oxygen — the basic recipe for fire.
  2. Open flame and high temperatures require extra vigilance. Go ahead, be paranoid – check everything twice or three times before leaving the shop. Take a play from the commercial pilot’s handbook and make a shop shutdown checklist if you have to.
  3. Keep your head in the game. My erstwhile colleague nearly burned the lab down in a moment of distraction. It was absolutely understandable in retrospect — he was going through a divorce at the time. But when you’re tired, sick, or emotionally compromised, it’s probably not the best time to be in the shop. Be safe, go read Hackaday instead.


Most modern smoke detectors are wired to mains or have a sealed 10-year battery
Most modern smoke detectors are wired to mains or have a sealed 10-year battery

Smoke detectors are almost universally required by building codes, and you’d think that more than 40 years after being widely and cheaply available to the mass market that there’d be no dwelling without at least one. Unfortunately, that’s not the case, and newspapers run sad reports every day quoting a fire marshall as saying, “There were no working smoke detectors in the house.”

Make sure your shop is covered by at least one working smoke detector. If like many of us you’ve been relegated to the basement for your hacking activities, don’t rely on smoke detectors on the upper levels to do the job, install one nearby. If your shop is in a detached building, you’ve got the extra problem of being out of earshot if the alarm sounds. Consider a WiFi-enabled smoke detector, or hack one together yourself. You can even IoT any smoke detector by simply adding a smart battery.

Fire Control

Despite your best efforts at prevention, you might face the day when a fire starts in your shop. This is not the moment to realize you have no means to fight the fire. You need to have the tools and the training in place long before the need arises.

You need a quality fire extinguisher suitable for the types of fires likely in the home shop. A quick review of the classification of fires:

  • Class A – Ordinary combustibles like wood, paper, trash, and plastic
  • Class B – Combustible liquids like gasoline, oils, or solvents
  • Class C – Fires in energized electrical equipment
  • Class D – Combustible and reactive metals like magnesium, lithium or titanium
New 5-lb ABC fire extinguisher for my shop.
Ansul Sentry 5-lb ABC fire extinguisher I just purchased for my new shop.

There’s also a Class K for cooking oil fires, but unless you’re hacking a turkey fryer that’s probably out of scope for the home gamer. In most cases you’ll be in the market for a Type ABC dry chemical fire extinguisher, in the 5- to 10-pound range.

Do yourself a favor and don’t buy cheap. A fire extinguisher is a life safety appliance, and that’s no place to economize. In general, the fire extinguishers available at big-box stores are junk. Rule of thumb: if the valve head is made of plastic (like in the banner image of this article), it’ll leak. Spend a few bucks more on a unit you know will perform when you need it. Most cities have at least one fire safety company that sells and services fire extinguishers; personally, I’d rather spend a little more money with a local company and build a relationship that’ll pay benefits down the road.

You’re also going to need to know how to use a fire extinguisher. It’s not second nature at all, and when it comes time to use one, it’s not the time to be RTFMing. At a minimum you’ll want to watch some good training videos so you at least have the basics. But nothing beats hands-on training. Your local fire service company can help there, although they may charge for live-fire training. You might also try contacting your local fire station; the firefighters will likely be more than happy to help you get trained.


When all else fails, you need to be able to get out of danger. Again, this takes forethought. You need to consider escape routes as part of your safety audit. Make sure you identify at least two routes of retreat, in case one route is blocked by fire. And don’t forget to practice your plan – in a crisis we tend not to rise to the occasion but instead perform at the highest level of proficiency to which we’ve trained.

Whatever your game is, if you’re reading Hackaday, chances are pretty good that you do something more dangerous than the average Joe on a pretty regular basis. Wouldn’t it make sense to be a little smarter and a little better prepared than the average Joe, too?

44 thoughts on “Hack Safely: Fire Safety In The Home Shop

    1. This, I was stood next to one of my motorbikes that caught fire when it backfired kickstarting it and lit the carb and someone hit it with a dry powder unit after a delay finding one and a argument who was paying for the refill ! (in a official ministry testing centre, not my home shop where I know where they are located). After struggling to breath as the user didnt give any warning he was triggering it and we all got a lungful of powder, it eventually was extinguished and I went on to feel ill for a couple of days, I know now I should have gone the ER or doctors… But that bike still had white residue on the engine for at least two winters use afterwards before I sold it.
      All my extinguishers here are co2. Much easier to clean up on the uber rare occasions I’ve had to use them. I’ve got one dedicated to the welding trolley, and a couple dotted around near doorways where I can grab them while making a exit.

    2. Only problem is CO2 can dissipate, and then if the target is still hot & combustible it can re-light, ask me how I know!

      Mind you, that experience led to my obsession with every shed and workshop having at least one extinguisher next to each exit.

  1. A decent storage plan for flammables goes a long way too, ounce of prevention & all. Things like not storing flash paper next to your hot end will keep your shed from exploding.
    Ideally you should have a proper flammables cabinet, but they’re expensive.
    Cheap stuff like baking soda or a bucket of sand does wonders as well but every kitchen and workshop should have an extinguisher. And don’t forget to inspect them and get them recertified as necessary.

  2. A benefit of going to the fire safety company is that, if they have good people, you can discuss the circumstances and get the appropriate extinguisher(s). Remember, you should plan to not need the extinguisher, and for it to be the right tool if you DO need it. Easy cleanup isn’t anywhere near the top of my list in selection.

    In my kitchen, I have a large, solid aluminum pot cover by the stove, as well as a small ABC. The ABC gets checked every month or so, and turned over (to insure that the powder is free) about every few months, as do the other dry chem units.

    In the shop, a 10lb and a 25lb ABC, a large water unit, and a small class D, and a fireproof blanket (used for heat treating and cooling rate control, but I keep it accessible as a fire blanket).

    Aside from gear to put out a fire, I do no hot work inside (it is not a fire-rated space) and big red buttons for cutting power to test gear and each machine. If I redo the power (modernize the panel, etc), I’ll put in an explosion-proof power relay and a couple cutoff buttons for centralized cutout to all but the lighting circuit in the shop space. As it sits, only the lathe has a magnetic cutout. The others are old-school.

  3. I had a massive gas leak on a new carburetor I was installing on a car, which got ignited by a backfire when I tried to start it. If I had not had a good fire extinguisher handy I’m pretty sure I would have lost the car, my garage shop and attached house. Ever since I’ve become the biggest advocate for having a fire extinguisher handy that you’ll ever meet. You should at least have one in the kitchen and another in the garage/shop area.

  4. Don’t use powder use co2
    If you set of a powder (dry chemical) inside, it will get into everything and I mean everything (most filters will not stop it) and damage everything.
    co2 being a gas will cool the fire and extinguish the flames. at best you will loose the hot end, at worse the who printer (if you are there to monitor it) but with powder, you will damage everything in the room and it will spread beyond the room.

    I looked into units that extinguish via a plastic hose that melts when exposed to heat but most are not rated above 100 degrees c.

    1. Arg, I mean cool the base of the fire ie the heat bed and hot end.
      I had a fire when the hotend sensor was ripped out of the hotend but not broken which of course meant that the hot end suffered thermal runway but wasn’t detected by the sensor!

  5. Spend a few bucks on the safety equipment everyone forgets – you.

    Read up on fire safety (there’s more to it than “don’t fan the flames”) that you won’t make the usual mistake of trying to carry a fire somewhere else. Think it through ahead of time – to pick up on the pilot’s checklist idea even private pilots have a shutdown checklist but the usual rule is that you have a checklist for something you do every day and have memorized plans for the things that almost never happen. Very counter-intuitive but when things get busy you may not have the time or focus to act properly from a list that’s lost somewhere – train your reflexes before you need them. Cf. “fire drill”.

    Also get a cheap fire extinguisher on sale (or going out of service or similar) and actually try using it. It’ll cost you maybe fifteen dollars, tops. It’s not rocket science but most people have never actually squeezed the handle on an extinguisher. If it’s CO2, you’ll have a lot of fun, if it’s powder you’ll make a mess so do it someplace tolerant of messes (hint…dumpster if you’re in an urban area). Once you realize the range etc. you have with those, you’ll be better at aiming at the base of the fire instead of just waving it around wildly.

  6. Three times I’ve had to use an extinguisher, and three times I’ve had the 1st unit I grabbed not be usable. I don’t know what a valid “service inspection” is supposed to consist of, but I’m convinced it is nothing more than signing the tag in the large majority of cases.

    1. If it were a powder extinguisher:
      you would have needed to bump the unit firm to the ground before use.
      Because over time the powder will densify at the bottom – the bump will loosen it up.

      The more vibration such a unit is exposed to, the more dense the powder will get over time.

    2. I work in the fire protection field, and that’s unfortunately the case with many inspection-only companies. They put in insanely low bids for buildings, so their techs usually just do what you’re saying. The company I work for is better about that, when we do extinguisher inspections there are a couple important steps.
      Check the gauge, check the manufacturing date and serial number against the record, unscrew the hose and check for obstructions, tumble the cylinder 3-4 times and listen to the powder to ensure it’s moving freely, then write out a new tag with the serial number and date.
      So long as there’s pressure and loose powder, they’re essentially guaranteed to work. In my jurisdiction the cylinders have to be serviced and have the powder replaced every 6 years, and the cylinders themselves have to be hydrostatically tested every 12 years.

      1. The last time the landlord sent an inspection company through my hackerspace, they silently walked off with the CO2 extinguisher in our laser cutter room. Apparently it was a bigger sin to have a fire extinguisher that wasn’t mounted to the wall than it was to remove it and leave a fire hazard unprotected.

        I was luckily on site at the time and noticed it before they left, so I went over and yelled at them until they replaced it, and yelled at them again when they tried to sneak a powder one in in place of the CO2.

    1. I love purple-K. Just don’t want it in my house. A number of years ago got a bunch of 5gal buckets from a supplier who couldn’t get rid of it (removed from extinguishers during service) for a flame cutting job in a fire prone (forest) area. It came in quite handy. Site owner wanted to buy the leftover. We “gifted” it to him. Amazing stuff.

  7. 2 cents from someone who has set themselves on fire way too many times…

    – dry powder extinguishers in cars are great, they need to be replaced every now and then. the powder packs down and “clumps”/becomes solid.

    – when welding
    – don’t do it alone
    – if you’re doing it outside, wet the area down, keep a hose handy or a water extinguisher handy
    – when gas welding, soldering or brazing, make sure all your fittings are tight, but not over tight
    – wear a leather apron
    – use good quality welding gloves

    when grinding be aware where the spark “plume” is going, grinding is hot and noisy, you can be well alight before you realise.

    be careful what you wear, I never wear synthetics. even crappy denim won’t burn that well. A really good quality lab coat is worth it, same goes for a shop coat or leather apron.

    if you do catch fire, don’t panic, “drop and roll, don’t run” is an ok strategy, but ripping off the burning garment is better.

    if burnt flush with water, keep it up for as long as you can. a towel full of ice works well.
    cover the burn with a clean, non stick cloth or in a pinch, paper towel.
    do not use any kind of “burn cream”, butter or anything else

    Get thee to an ICU, with all haste, do not tarry!!!

    1. Leather apron also saves clothes from holes caused by burning sparks. You can wash out dirt/grease but holes are trickier.
      One thing many forget. Make safety /easy/. I have my apron, shield and ear protection hanging just inside the door, so they can be grabbed on the way in and put back on their hook on the way out. They are always in easy reach. Having to hunt for safety equipment makes one more tempted to go ‘Oh, it’s a quick job, won’t bother this time’.

      And fireproof workbenches! I have two, a big sheet of 15mm thick steel plate for when I want a conductive bench or to tack things to. And my favoriate is a long bench made from 20mm compressed fiber cement(Same stuff they use under tiles in bathrooms on second floors).
      Very hard for fire to get out of control when you have safe places to put red hot metal.

  8. “But when you’re tired, sick, or emotionally compromised, it’s probably not the best time to be in the shop. Be safe, go read Hackaday instead.”

    Burn something ELSE down. :-D

  9. To add a little bit more to it, if shit really hits the fan, dont try to be a hero and try to save some expensive equipment from the fire. Putting your life at risk is not worth it for something that can be replaced with time and/or money. At the same time, if you feel like the situation could get out of hand, dont hesitate to call the emergency services first, give them the information they need (who calls, where is the event, what is the event, how many people are involved / in danger, …) and then start to get people (your family that is in the house next to the garage you set on fire,…) to safety before you try to maybe do something about that fire.
    I know, its probably hard to decide when it is better to quickly grab an extinguisher and starting to fight a fire yourself, and when it is better to first make shure everyone is safe, emergency services are informed and then try to fight a fire. I guess it really depends on your place and how quickly a fire could get out of hands.

    1. “It’s a nice shade of red and gives me a feeling of safety.”

      “Disappointed that the trigger and nozzle wasn’t more sci-fi raygun looking, but plastidipped it to de-uglify the stamped steel and it’s bearable now.”

      “Just the right weight to hold open the shop door.”

  10. And don’t keep the fire extinguisher too close to where there’s likelihood of a fire. A friend stayed for a few days living in her camper parked in the backyard. Thanks to a gas leak her gas stove caught on fire. Where was the extinguisher? Right next to the fire of course. Lucky for her I had one in the shed which quickly put the fire out.
    Another friend was driving a garbage truck when he heard what sounded like an hydraulic hose bursting. He pulled over and found the hydraulics already on fire. Where was the extinguisher? Right next to the hydraulics of course. The only thing he could do was stand back and wait for the explosion. No more garbage truck.

  11. “the latter tragically claimed the life of a 17-year old lad with a lot of promise.”

    No, the giant pile of improperly stored pyrotechnics in the same area did that. You’re not Facebook, you stop with the repeated sharing of bogus news stories.

    1. Look, I’m getting sick of this crap about it being a bogus fake-news thing. A bogus new story is something that did not happen, while this quite clearly and dramatically is something that happened. My original article has links to the local fire marshall (or whatever they call it in Britain), a trained fire investigator who made the determination by examining actual evidence at the actual scene of the actual fire and concluded that the 3D printer and the hairspray were the proximate cause of said fire. Sorry, there’s nothing bogus about that.

  12. It’s good to know that the fire extinguisher you get needs to fit the classification of fire types that you may face in your home. My wife and I were looking at getting a fire extinguisher for our pantry in case a fire ever breaks out in our kitchen. It seems like an ABC extinguisher would be our best option to pursue.

  13. A friend of mine recently had a small house fire in his kitchen, and because of that I have been very worried about a house fire in my house too! I really appreciated the advice to have multiple smoke detectors in the house, especially in my home shop. I will have to find some cheap affordable smoke detectors to ease my worries!

  14. Something I really miss are smoke detectors designed for (almost) deaf hackers. I work in a place with chemicals and ultraviolet class 4 lasers, so I combine great care and laser goggles with a shutdown procedure and cutting mains to unused devices; but at home, there is no way for me to detect a fire while sleeping.

  15. I know this is an old article, but i somehow found it and i wanted to add some information: In Europe the fire classification system is NOT THE SAME! Class C is gas fires (i mean like butane, propane, methane, not the stuff you put in your car), not electrical fires. For those there was a class but i think it does no longer exist. Also cooking oil is Class F, not K.

    Also, as said, don’t use dry powder indoors. It will make a HUGE mess. In Europe there a “ABF” extinguishers that use water and some foam agent, much better and will work on cooking oil to (where a dry powder extinguisher won’t). Of course they do not work for gas, but gas fires should be extinguished by closing the right valve or left burning, because otherwise you will get an explosive atmosphere and thats worse than a fire (you can see the fire, you can’t see if there is a risk of explosion!).

    Uh and NEVER NEVER NEVER use water on an oil fire. Ask Youtube if you don’t know why!

  16. Thank you for mentioning that your neighborhood fire department can assist there, but they could charge for training with actual fire. For her home, my mother says she wants to purchase an Ansul suppression system. I’ll arrange for a local service provider to provide her with live-fire training.

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