As my laser build starts taking shape, I’m trying to decide what size CO2 fire extinguisher to buy for it.
How big a CO2 fire extinguisher did you buy for your laser cutter?
What size would you buy if you were doing it over again, and why?
TL;DR: The 5lb / 2kg class has been overwhelmingly recommended.
I must check at the makers tonight to see just what fire extinguisher we have. Hopefully not a dry powder type, I’ve seen what they can do to the inside of a laser cutter (not a cheap K40 either!)
Michael… I guess it depends on how big of a fire you expect… I have also determined that a c02, or preferably a halon extinguisher is a must. Dry extinguishers were never on the list. I think anything that can produce enough volume to fill the machine with gas should stop anything, assuming the fire is not reigniting.
I’m looking at a 2.5 lb. model or this 1.4 lb model. Small price difference, but size might be a factor.
Halon is proven around electronics, enough air to breath but not enough for fire to burn. At least in MHO that’s the direction I’m leaning. (8’)
I have very strong opinions regarding Halon.
Halon production was banned in 1994 as a potent and long-lived greenhouse gas, and it’s toxic. It makes sense to use halon for applications where there should never be a fire (e.g. on board aircraft) and any fire is an immediate threat to life, but I think it’s not appropriate to use it where a fire is expected to be likely in normal operation, as with a laser cutter.
I neither want to contribute to global warming by unnecessarily releasing a greenhouse gas, nor wish to expose my family to toxic gas. One reasonably likely reason for a flame-up would be if the exhaust fan fails, which would mean I would be concentrating a known toxic gas in my house. My data center training included that if the halon release alarm sounded, drop everything and get out the door immediately to avoid breathing it.
CO2 won’t damage the laser cutter, and is normal for use with laser cutters. I think that environmental and financial cost are two very good reasons for this normal.
My intent is to get one that is large enough that I can put out a fire before it damages the laser cutter, and still have enough left to use again to keep using the laser cutter in the same session, before getting it recharged.
Good point about it’s a greenhouse gas problem, one I didn’t know. When I went through the training as a field engineer working almost entirely within computer facilities they never mentioned anything about it being toxic. In fact they did have a room for us to go in an breath it to show us you could breath… Of course that doesn’t mean it wasn’t killing us… 
Most of those applications were low concentrations levels. But as you point out it’s manufacture was banned in 1994 because it’s ozone depletion is apparently massive. Count this one out… Funny these are for sale, usually when the production is prohibited the use is also prohibited.
My only reason to depart from CO2 was that the it caused a great amount of moisture to condense when it was released and I replaced many boards that were damaged by CO2, according to the customer. Halon also can cause burns from cold, but I never saw the condensation. Don’t see how it could be any different. Maybe I wasn’t observant enough.
My area was in the desert southwest and the humidity is in the single digits most of the time so it seems like ti would be more of an issue in humid areas. I’ve been out of the field for 30 years… if that indicates anything…
I think you could flood a laser cabinet with very little co2, especially if you could trigger it with the covers closed.
I had no doubt that I had to have something for fires… Glad you started the thread… Hope for good suggestions… Take care…
My data center training was around the turn of the millennium, was probably less detailed (I was responsible for part of a lab) and I have no idea whether my training was industry standard. I’m curious, though; what kind of boards were damaged by water? I remember around the same time you are talking about, the advice was “shower with your keyboard” to clean it. I heard of cleaning flux off circuit boards in a dishwasher dedicated to the purpose. Was there some sort of environmental contaminant such that an acid or base created a corrosive solution or something like that?
I did think about an integrated system plumbed into the air assist and even thought about trying to automate it. My enclosure is about 750 liters. It looks like CO2 is a little less than 2g per liter at atmospheric pressure. Ignoring stoichiometry for a moment, if replacement were perfect that would be around 375g of CO2. A 24oz CO2 paintball canister would be nearly two full changes of air (680g). It wouldn’t be a perfect change, but then as long as the stoichiometry changes enough to not support combustion for a bit while it cools down (helped by expanding CO2) that’s probably OK?
But I’m guessing that I’d need a lot more than that if I have the lid open. Therefore I was thinking about 10lb as a reasonable size portable fire extinguisher.
I’m assuming that a fire could be bad for the optics and if I have a fire there’s a substantial chance that I’ll be replacing lens and/or mirrors if nothing else.
Most of the time the problems were in peripheral equipment such as tape handlers and disk drives. In one instance a fire was near a tape handler and they used their CO2 on the fire. The closest handler had multiple card failures the ones on each side each had one card failure. I still have trouble connecting that incident because the cooling was cold air coming from under the floor up into the machines. This should have eliminated most of the CO2 that was in the area. Compared to everything else in the area the gas was release in the low pressure area, never should have reached the machines innards anyway.
I could see where the ‘smoke’ had left the IC, but nothing else was there. I ran this up through engineering where I worked as to why we had so many failure with CO2 extinguishers. Initially told it was condensation. Never did get an answer. They went to Halon, so you could get out of the area, and it wasn’t an issue any longer.
I believe you’ve got it right, except for opening the door. A few nozzles on the inside and a short burst, the whole cabinet won’t support combustion.
I don’t like opening doors with burning things inside, you’re always adding that little bit of extra oxygen…
When I was a police officer, I always thought that firemen were nuts since they ran into a burning buildings, they thought we were nuts because we went after bad guys who shot at us…
Combustion products are often corrosive, I’ll put my money on that. I wonder if a Halon flood just extinguished the fire faster than hand-held (?) CO2? 
It’s not an exclusive choice. A hand-held extinguisher is a non-negotiable item; integrated fire suppression is optional and not on my list for first light. (Though I do have an unused 24oz paintball CO2 canister for reasons that don’t involve paintball.)
Also, this is made of aluminum extrusion, so there is a lot of room for air to get in; it’s not really airtight, so more O2 will get in even with the door closed.
I’ll keep thinking about an integrated system, though.
(Maybe I should make one of those new DIY O2 concentrators, and then use O2 as cutting gas and the N2/CO2 mix left over as shield gas. 
)
Enough flow for enough time and any leaks won’t matter… 
Quite right about no reason you can’t have both. I’m sure I’ll have a hand held long before an ‘installed’ ideal system. Although it makes me wonder how horrible could it be for a diy project? Wonder what it would cost to set up an emergency controlled ‘burst’ of CO2 system.
Sounds like right up your alley (8’) Can’t wait to see how you solve it… 
And now we’re back to the original topic!
After all the You must buy a CO2 extinguisher for your laser advice here I was rather expecting that someone would own up to having, you know, actually bought one. And maybe have an opinion about size… I’m running into the same problem on twitter, too. 
I’m doing my best to keep the thread alive, but no takers (8’)
Isn’t that how it seems…catch 22
Looks like about any CO2 extinguisher is around $150+ for 5 lb. I have found some used ones on ebay, but it seems they all need a hydro test and recharge for just over $50 bucks.
Here’s a link to the wiki on Halotron I, Halon replacement and is still manufactured. But, again, the costs appear to be double that of CO2 based on weight.
In the PD we used and were trained on lots of different types of extinguishers and most seem to me they were what I consider ‘binary’ valves, either open or closed. I think you’d be hard pressed to control the output at 1/2 just by the by the handle… IMHO…
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Spoke to a fire extinguisher company locally. He advised that I should not purchase one that isn’t operational when purchased. He stated lots of these were aluminum and require a new head and seal. Plus many have been recalled. What surprised me was that he couldn’t get any of the extinguishers at this time due to covid-19 issues.
He advised the lowest price is at Web Restaurant Store. Found this 5 lb model for $108 and a 10 lb one for $160. The 15 lb model is $185. Lowest cost of these anywhere I’ve looked, don’t forget to add about 1/3 for shipping… (:O)
My honeycomb bed was about $80 plus about $100 shipping. I had been assuming that I would order online, but also there is a restaurant supply store near me so it’s probably worth my while to check there as well, it would only cost a phone call. Then I could probably try hefting them to think about how easy it would be to use.
That’s what I did after the fire guy told to check them out. The local one doesn’t have anything below 15lbs and even the 5 lb one was lower cost online even after shipping. I cringed at the 30+ bucks to ship a 108 dollar item. But it’s a tank, fortunately it’s made out of aluminum.
I was a certified scuba diver at 13, back in the 60’s and steel tanks were the norm. I must have been about the weight as those tanks. I remember getting a new 50 cubic foot (about 1/2 the normal size height wise) tank and it was aluminum. It was really great to be able to crawl up the ladder on the boat get out of the water and actually walk upright.
At least at this point I’m not so worried about fire…
What do we have to do to wake this thread up??? We can’t be the only ones going down this road…
Wonder how long a tall or big commercial CO2 tank would last as an air assist source. I don’t know enough about what kind of volume you need to even try to figure out if it’s feasible, cost wise. It would also ensure a dry source. Probably be very effective at keeping the flames down when cutting.
CO2 Laser Machine Fire Suppression System
Sort of what I was thinking… During the summer it’s 110 a lot.
I guess I don’t need one if I’m watching it… (:O)
That even got to my Integrated fire suppression? idea, very cool. That’s simpler than I had thought of. I’ll ponder that!
Thanks for you viewpoint… Kind of hoping the one I ordered is never needed either… Seems like when you have insurance it doesn’t happen, so I think that’s reason enough. Also built my table out of metal, less likely to catch fire
I have my 5 lb next to the laser. It was damaged in shipping and I took it to a local extinguisher place and they fixed it for $15 bucks. Lost the receipt on the way home. Advised the merchant that I had it fixed and they advised to send the receipt and they would reimburse me. I told I didn’t have it, but thanks anyway.
I received an email that they are returning 15 bucks back to me for the incident. Stating it’s policy was ‘waived’ this time. Nice company to deal with. Web Restaurant Store.
Kind of hoping that buying one, having it there, will, in itself stop any fires. (8o)