Fire Extinguisher for CNC?

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Wow did I fall down a rabbit hole. It started when I learned the phrase “clean agent fire extinguisher”, after hearing that if we used a regular “foam” fire extinguisher we would probably destroy our CNC machines. The claim was that the foam would most likely destroy the electronics, and possibly damage more since the foam leaves a residue that can’t be cleaned up.

Prepare for sticker shock. While a foam fire extinguisher is under $30, this is the cheapest CO2 fire extinguisher I could find ($208).

Then I watched this (somewhat redneck) but entertaining video where they tested fire extinguishers that left me even more disappointed and confused.

Now I’m wondering if the best option, assuming you are actually present and watching your CNC, is actually a fire blanket big enough to cover a Shapeoko? With an inexpensive foam/traditional extinguisher as a backup.

Curious to hear the community’s thoughts.

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“An ounce of prevention…” :wink:

Keep it clean, watch & check your tools for heat. You want them running cool for other reasons than fire hazard. Keep flammable solvents away.

The CO2 extinguisher is also good for other areas of the house/shop. So it’s not a dedicated cost to the machine itself.

But the foam extinguisher & fire blanket is a reasonable backup plan.

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Not a fire expert, but I did go ask a bunch of these questions before buying extinguishers for my workshop and I have put out quite a few electrical fires over the years on low and higher voltage equipment, so, here’s where I got to, very happy to be corrected by actual experts.

The foam and powder are both nasty and tend to leave you with a lot of cleanup or replacing things, however, if it’s already on fire you should ask the question of what is more important, putting it out quickly and reliably or trying to minimise extinguisher damage. There’s nothing that says you have to dump the whole extinguisher even after the fire has gone out.

I might be tempted to use an ‘electronics safe’ extinguisher for things like the VFD which might go woof, however, they tend to just let out magic smoke, unless they’re full of sawdust and have been enabled as a proper ignition source.

Water or foam on things with 110 / 230V I would want to knock out the power first. Low voltage stuff like the controller and steppers, you’ll probably kill the electronics, but, if it’s already on fire… If you’ve got a good EPO to drop power to the whole machine then that should assist in safety and damage to LV electronics.
Beware - on a VFD powering it off does not kill the internal voltage and depending on the fault mode there could still be 400V inside the VFD, I would not want to use a conductive extinguisher there, CO2, powder or blanket are good safer options there.

Fires on the machine are likely to be more easily handled and local than a fire in, or which propogates to, the dust collection system, which is likely to need higher volume extinguisher which is optimised for paper / wood type fires. Whether you have an enclosure has an impact here, if you open up with a CO2 extinguisher on a spindle / router fire in the chips on the workpiece you may just be distributing the fire, whereas if you have an enclosure you can fill the enclosure with CO2 (after shutting off extraction), close the doors and wait. - edit - the inside of your enclosure would want to be plain plywood or similar, not a light flammable foam or other coating which could cause rapid spread.

After lots of reading, pricing, being told that I needed a whole wall full of specialist fire extinguishers to allow me to choose the right one for the fire I’m currently experiencing etc. I ended up buying a couple of these

A small one and a 5kg for small fire and a ‘panic’ fire version. I accept they will make a nasty mess of whatever is on fire, but if it’s more than magic smoke from the electronics, I think I want the fire put out first and I’ll do damage assessment later. They claim it’s safe on electricals but there’s also an old kitchen fire blanket for the VFD if it goes woof, I try not to let it fill up with dust. The rest of the 230V power is all in a metal switchgear cabinet which can burn inside as much as it likes.

HTH

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I have both an ABC extinguisher and a fire blanket mounted nearby.

As @LiamN said above, if the thing is on fire, my only priority is to put it out - and the state of my machine is going to be in question, anyway - so I’m not particularly worried if the machine suffers because of the fire remedy.

That said, my plan is to try the blanket first, if possible. If that doesn’t work, the ABC extinguisher (dry) is next. If that doesn’t work, I plan to herd the sheep and get the flock out of there!

  • Gary
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The dang thing is a $2800 pro xxl. The shop is 20 times more expensive to lose, probably more. At that point I don’t care about controllers, cheap computers, and misc. electronics. I have two extinguishers and a fire blanket. I am putting that fire out right now.

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Agree with others, “saving money” trying to stop a fire doesn’t matter if you don’t save your shop. Put the fire out by any means possible.

That being said, this is an interesting discussion and reminded me of a product I saw xTool selling for their lasers, a fire detection and suppression system. Uses flame sensors to cut power to one of those smart switches, and then has CO2 cylinders that flood an enclosure to smother a fire. There are conceptually similar products for larger industrial machines that run lights out, or cut materials that burn or use oil based coolants.

Not sure any of it is applicable to an open gantry-style router, but thought they were cool.

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Hey Winston - that’s an interesting device - I wonder if they make a bigger capacity unit - because it says that it’s designed for enclosures that are <.13m3, which is about 7900 cubic inches - which, if you assume, say 24" as the height of a Shapeoko enclosure, would limit the xy of the enclosure to around 18x18. Is that right? Someone check my math…

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The volume limits they post are probably due to the amount of Co2 they are using and the length of the sensor wires. Someone with the skills could adapt this for a bigger work volume.

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Gas purge to reduce O2 levels below the level required to sustain a fire is a pretty well accepted approach. It’s one of the three legs of the fire triangle, heat, fuel and oxygen.

I have seen a number of facilities with low oxygen systems deployed to entire rooms or buildings to prevent fire from being able to take hold and damage critical equipment, either directly or through the deployment of fire suppression systems Hypoxic air technology for fire prevention - Wikipedia
I’ve also seen inert gas purging systems in some smaller enclosures to prevent fire in places you really don’t want a fire, such as CO2 and Nitrogen gas, which bring the benefit of rapid cooling as they expand from the pressurised storage, hacking off another leg of the fire triangle stool. Note that the violent insertion and expansion of the gases coupled with extremely rapid temperature changes are frequently terminal to the electronic equipment in these cases, it’s about fire containment and the outlet may be vented out of the controlled space similar to an arc-flash venting duct.

There are also agents which chemically block part of the fire process, halon is largely banned now (but still used on planes and in the channel tunnel apparently) but there’s a bunch of replacements such as FM200 etc. which are all deployed at high flow rates into a space. These have issues including cost, cost and also cost, but also damaging levels of noise.

The differences with a CNC enclosure that immediately spring to mind here are that we don’t typically install fire dampers on the dust extraction system to close off that airflow, or vent dampers to allow gas expansion out of the enclosure during a deployment of the fire suppression.

It might also be worth noting that in many of the facilities full of expensive computer equipment we have gone from FM200 and other expensive gas systems back to zoned sprinkler or water mist as these are much cheaper, at least as effective, easier to recharge and, interestingly, so long as you don’t allow puddles to develop, frequently don’t do that much damage to the equipment. Clearly one seeks to cut off power prior to deployment but in many cases now we have Lithium based batteries in the space and the prevention of a fire spread from these is a key driver for going back to sprinkler.

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I have a CO2 fire extinguisher, alarms, security camera and Insurance along with photographs of my shed and receipts. The shed is a distance from my house so family and main belongs are safe. Im probably more likely to have a tree fall on my shed during high winds. :slight_smile:

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This past winter (while I was waiting for my 5Pro to arrive), I was using my table saw and smelled smoke. I killed the power to my saw and dust collector. By the time I got my extinguisher (a dry chemical, which I keep hanging by the door to the shop) there was smoke around the throat plate. I discharged the extinguisher, and grabbed my second one. As I was checking the saw and dust collection system, my thought was ‘darn, that ext. agent ruined my saw’. Nope. After I cleaned up the mess and vacuumed all the sawdust from the saw, I couldn’t find anything wrong with the motor. I just put a clean, sharp blade on the machine. I found a pitch pocket on the board I was cutting and burn marks on the blade. Lesson learned. Keep cutters and blades clean and sharp (I use an ultrasonic cleaner). Pay attention working in the shop. It’s only a machine, it is replaceable.

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I was running my surfacing bit on my S5Pro about a week ago. The bit ran the length of the board and towards the end it would start the make a bit of smoke. I babysat that machine and slowed everything down until I was able to get thru the cut. The bit was dull and finally ready to be retired. So, I agree with you able keeping an eye on tool life and having clean sharp tools to cut with.

My biggest issue was that bit was the only one I had and I needed the piece finished so I could finish putting together the backsplash I was creating for it. Could have been a disaster if I kept trying to push the tool. Me reading this thread has got me really thinking big on my fire safety procedures. I have one fire extinguisher and it is in my truck right out front of the shop. Thinking about redesigning the power supply, fire safety protocol, fire blanket, and extinguishers.

If my shop went up in flames, I would lose my whole work life. It has everything in it. This is a scary thought.

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There are Halon variant gas extinguishers that work. Pure halon was banned years ago but there are variants available; it’s all I use, shop, cars and in house. I had a fire in our oven years ago, 1 squirt, no more fire, no mess.

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