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I'm planning to make a small DIY gas tank and I saw people using old or used fire extinguishers but I don't understand why my fire extinguisher can't hold pressure after one use.

I have this fire extinguisher about 3 years and it was holding pressure but few weeks ago my home workshop caught fire from a lithium ion battery explosion. I used my fire extinguisher to control fire but I only used a little bit. After I used it the pressure gauge showed half of the pressure remained but after few weeks pressure slowly leaked to zero.

Do all fire extinguishers do that or is mine just a cheap one?

Also I must add: My fire extinguisher is refillable (instructions say it can be refilled by the manufacturer). I'm thinking maybe they have a special method for locking the mechanism? Because leakage happened after I removed the safety pin. Maybe the company added a mechanism so people have to send their fire extinguisher to the company after use?

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    "Gas Chamber" is probably an unfortunate translation error because I hope that's not what you are making... – JPhi1618 Sep 12 at 3:54
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    It's probably translation error , I'm planing to build Co2 tank for my aquarium (citric acid + sodium bicarbonate chemical reaction) I'm using coke bottles but they can't hold much pressure , I thought fire extinguisher would be better – Mordecai Sep 12 at 4:27
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    If you're just looking for CO2, you may be better off getting a CO2 tank from a store that sells welding supplies, or one that supplies CO2 for other commercial uses (e.g. used in almost any bar for beer kegs). You can get CO2 canisters in a variety of sizes, basically all are intended to be refillable, and all of them use valves and regulators that allow dramatically better control of pressure and flow. – Makyen Sep 12 at 15:51
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    Just as a clarification on proper use: Unless you witness a small fire start and you can immediately use a Fire Extinguisher to put it out, a Fire Extinguisher's main purpose is to create an opening so you can flee the area. IE if your kitchen counter is already blazing and your cabinets are starting to catch, leave the area. A "Fire Extinguisher" is likely not going to be able to extinguish the fire before it is empty. – Michael Richardson Sep 12 at 16:14
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    @R.. pop bottles have no means of gracefully handling over pressure and when tossing dry ice in you can easily overdo it. It's dangerous compared to using a proper pressure vessel. – whatsisname Sep 13 at 6:05
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If it's a dry chemical extinguisher (seems likely, most common, particularly with a pressure gauge) the simple answer is that the valve has got dry chemical dust in it and no longer seals properly as a result. When refilling the valve or valve parts will either be cleaned or replaced as needed, the dry chemicals will be placed in the container, the valve installed, and clean gas will be added to pressurize the tank, which will not contaminate the sealing surfaces of the clean valve. When you discharge the extinguisher, powder and gas both flow out through the valve, and some powder stays in the valve. Leaks ensue.

The instructions on the side of the (refillable, servicable) ones I have state that they should be fully discharged and then professionally refilled immediately after any use. So the above would not be an issue.

If you want an extinguisher you can partially use (and particularly if you are building a CO2 tank) look for a CO2 extinguisher. They don't typically have gauges (since a gauge would only tell you what the temperature was) - you weigh them to see how much is left. The instructions will still want you to refill after any use (because that's how fire extinguishers are always labelled, to be ready in the event of a need at their rated capacity) but practically speaking most CO2 extinguishers will reseal (there is no dust, just gas) and if you have a clearly labelled "normal" extinguisher and a CO2 that you label as "not for use as an extinguisher" you could do that - or you could just get a small CO2 tank that isn't an extinguisher at all, which would be even more clear.

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    CO2 extinguishers are rather dangerous if deployed indoors by untrained users.... a full size CO2 emptied in a small room is likely to make a literal gas chamber of it. There is a reason these extinguishers are only found where absolutely needed. – rackandboneman Sep 12 at 21:17
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    @rackandboneman: Fortunately, unlike most other asphyxiant gases, CO2 does trigger the hypercapnic alarm response (i.e. feeling of suffocation) in humans, so at least you'll know that something is wrong. (Of course, being trapped in a small room that's on fire is already likely to trigger hypercapnia and panic all by itself, so you may or may not realize that the extinguisher is making it worse. But at least your instinctive reaction will probably be to try and get out of there and into fresh air as fast as possible.) – Ilmari Karonen Sep 13 at 7:56
  • @rackandboneman and people expect it to be like movies and tv and make for a fun prank but end up getting a nasty green powder all over your dorm room instead of a hilarious puff of gas. :( – Captain Man Sep 13 at 18:28
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    I've kept a CO2 extinguisher with my welding kits, ready for a short squirt at the end of the job, just to make sure. Never had one fail to squirt after being part used. Good for errant dogs and hornets, too! – Tim Sep 14 at 16:10
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    Thanks for answer , I never thought of that . I will try to clean dry powder , Can you recommended any cleaning methods ? (I'm thinking about , first water then pressurized co2 ) – Mordecai Sep 15 at 5:38
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Fire extinguishers (here in the US anyway) are REQUIRED to not be usable after being discharged, partial or not, because you can never know HOW MUCH extinguishing material was discharged by just looking at the pressure gauge. So the valves are designed with breakaway seals that, once broken, will not hold the charge for very long, forcing you to replace it or have it recharged and re-certified by the manufacturer. These are devices used in saving lives, it's all very serious from their perspective.

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    Do you have a reference for this law/regulation? I can't find it referenced anywhere. I'd always heard that after use, the valve in a disposable fire extinguisher doesn't re-seal well so it will lose pressure, but assumed that was a manufacturing convenience, not a requirement. Even rechargable extinguishers are required to be inspected after use (after the seal is broken), but I've never heard of a requirement that they are intentionally designed to leak after use. – Johnny Sep 12 at 14:43
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    Required (for legal & life safety reasons) to be serviced/refilled/recertified, yes. Required to not be usable - uh, no. "Gosh, I squirted the fire extinguisher on this side of the fire, stopped, went to the other side of the fire and it wouldn't go again" I Think Not. – Ecnerwal Sep 12 at 15:36
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    @Ecnerwal, I read it as it would leak down over the next several hours so someone wouldn't hang it back on the wall and expect to use it again next time with who-knows-how-much life left. Citation would be nice tho. – JPhi1618 Sep 12 at 15:54
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    -1 As a member of NFPA, I find NOTHING in NFPA 10 manual here on my desk that says that it is required to not be usable after being partially discharged. The closest I find is a warning in section F.5.4 to make sure to have it "...refilled or replaced promptly..." because "...the extinguisher can lose the rest of its pressure." (emphasis mine) – Keeta Sep 12 at 17:57
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    @BlueRaja-DannyPflughoeft As OP said, "half of the pressure remained but after few weeks pressure slowly leaked to zero". If it takes you "a few weeks" to put out the fire, then A) Your extinguisher should be long empty and B) Why haven't you called in Professionals yet? – Chronocidal Sep 13 at 13:29
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While not strictly speaking "single use", I would consider a typical consumer-grade residential fire extinguisher (I have 2 - one on each floor, with the upstairs one near the kitchen) to be a single-use item. This is for a few reasons:

  • Even a moderately sized fire could make good use of the entire extinguisher, so if it is "half used" it is already in the mode of "possibly not enough for when you really need it again".
  • While the main case is pretty simple and sturdy, the firing mechanism has more small (and possibly plastic) parts and is therefore likely to have problems after use. Remember, that one use in a fire involves pushing a lot of chemicals at high pressure through a small mechanism very quickly - easy for that to cause damage to the mechanism.
  • The price ($15 - $50 typical in a quick search) doesn't allow for super-high-quality mechanism, so it is "just good enough to do the job".
  • Because the price is low (which encourages people to buy an item that they will hopefully never use!), it is not cost-effective to professionally recharge these fire extinguishers, which means the mechanism does not need to be designed for multiple uses.

You may ask:

If this fire extinguisher is only going to be used once, why bother to have any pressure gauge on it at all?

The answer is that because there can be leaks for other reasons - e.g., fire extinguisher dropped but did not activate, corrosion of parts, etc. - the pressure gauge provides an easy way to tell very easily whether the fire extinguisher is likely to be functional when it is really needed.

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    What I'm saying is that for typical residential extinguishers, they don't refill them at all. – manassehkatz Sep 12 at 5:34
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    @Mordecai:$1 per refill? Where in the world are you? That is way cheap. Instead of using a fire extinguisher, use a CO2 bottle. They make 5 pound CO2 tanks that I have used for my live plant fish tank. Call your local welding supply house, or ask a restaurant where they get their CO2 from for their beverages and buy the correct tank. – Gunner Sep 12 at 9:47
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    "The answer is that because there can be leaks for other reasons" - And let's not forget that it clearly marks extinguisher as used, very important for single-use life-saver! – Mołot Sep 12 at 14:33
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    @Mordecai, the mechanism isn't so much "fragile" as "inherently single-use". The biggest challenge in designing a fire extinguisher is coming up with a valve that can hold pressure for ten years or more. The most common way to do this is to glue, weld, or otherwise permanently affix a seal across the end of the pressure vessel; activating the extinguisher breaks the seal and leaves just an ordinary, leaky valve holding back the pressure. – Mark Sep 12 at 20:08
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    @cbeleites, I just checked the instructions for my home extinguisher. It needs to be inspected every month, but that inspection consists of ensuring the nozzle is clean, the tamper seal is intact, and the pressure gauge reads "full". Nothing about servicing, presumably in recognition of the fact that almost no homeowner will actually have the service performed. – Mark Sep 15 at 19:30
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Fire extinguishers with plastic heads cannot (or should not) be refilled (recharged)...only metal heads.

Plastic heads can split, crack, etc. over time. Either they won’t take a charge or they’ll loose a charge over time.

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    I checked my fire extinguisher , head part made of metal (I don't know what kind of metal but non magnetic and conductive) but metal part's hole made of plastic . Also I noticed something : fire extinguisher have a seal maybe seal automatically vents gas to prevent reusing ? – Mordecai Sep 12 at 4:24
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    Translation mistake , Seal => safety pin – Mordecai Sep 12 at 4:31
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Just a warning:

An accident with kilogram amounts of pressurized CO2 in a constrained space could turn that space into an actual "gas chamber" - there could be injuries from losing consciousness and falling, or even death or permanent damage from choking.

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    @RobinBennett It is not the displacement of air that is the problem - it is the fact that CO2 is acutely toxic at higher concentrations. Excess CO2 in air is absorbed by blood as carbonate. It makes the pH of your blood drop, and that causes severe issues with the ability of blood to function as electrolyte for oxygen transfer AND it causes hypercapnia - a range of serious mental disabilities (panic, hallucinations, irregular heart rythm). If you have ever hyperventilated yourself into a high, that was a very mild example of what you can eperience. 1kg in a room is certainly enough. – Stian Yttervik Sep 13 at 8:46
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    Great comment, but not an answer. – Matthew Read Sep 13 at 14:45
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    @StianYttervik To add, this is partly why exhaling lets you hold your breath longer. – Captain Man Sep 13 at 18:30
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    @StianYttervik, a kilogram into a small room will give you a concentration in the 5%-10% range. Pulling up a random MSDS, the 15-minute exposure limit for CO2 is right around 5% -- yes, you want to evacuate the room, but it won't kill you before you can get out. – Mark Sep 13 at 20:52
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    @StianYttervik, I'm not taking them lightly. I haven't experienced high-concentration CO2 atmospheres myself, but if OSHA says you can safely stay in a 5% concentration for 15 minutes, that means you can stay in a 5% concentration for 15 minutes without experiencing any life-threatening symptoms. – Mark Sep 13 at 21:44
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There are (at least) two types of fire extinguishers, ones that are preloaded and ones that you must load before use. The ones preloaded have the chamber, that contains the extuingishing medium preassurized. The ones you must load have a small gas tank and when you want to use the extinguisher, you press a button that releases the gas in the tank with the medium. Possibly you've got an extinguisher of the latter kind and the medium tank is not made to keep the preassure for a long period. Hint: if the extinguisher says one has to load it by pressing a button or the handles prior to use, this is probably the case.

Source: fire protection training in Germany, possibly fire extinguishers in the US work differently.

  • These "press button first" extinguishers have the advantage that they're easier to service. Fire extinguishers should be serviced every so often, and for an unused extinguisher the service will replace the gas cartridge without the need to deal with powder/foam under pressure. (also Germany here) – cbeleites Sep 15 at 12:51
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Can't help you with arts and crafts reuse, as that's off topic here. Do hydrostatic test the tank to 225% of working pressure. Better to go "tink" than "BOOM".

For use in a home,

Take the extinguisher to get it refilled

There are shops which do this, because commercial enterprises have their extinguishers refilled every few years. Extinguishers expire, after all.

Regardless, you should refill it because you partially used it, and extinguishers are designed to be used on a single fire. The on/off isn't so you can use it on later fires, it's so you can use it efficiently to attack the same fire.

Some low-end extinguishers are not refillable, and are indeed one-shot devices. If that's so, the refiller will tell you that.

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    I think you don't understand what I have asked . I'm not going to use this fire extinguisher , I already bought new 10kg fire extinguisher . I just want to use the old one for my diy projects – Mordecai Sep 15 at 5:30
  • @Mordecai That question is off-topic here, because diy.se's subject matter is home improvement. If you thought it was for general DIY crafts, that's an unfortunate naming issue with the stack. Fire extinguishers are only on-topic in the context of their use as a fixture in a home, As such, that is the only part of the question answerable here. – Harper Sep 15 at 6:16
  • @Harper He is building a Co2 tank for an aquarium. That's a fixture in his home so it's definitely on-topic. Don't gatekeep this site just because you only read the title of his question and not the contents and comments. – Navin Sep 20 at 3:59
  • @Navin Welcome to diy.StackExchange. You might want to [take the tour] and learn what our subject matter actually is here. That way you can be more certain when you claim something is "definitely on topic" and that others are "gatekeeping". Although I can't imagine how merely limiting my own words could possibly be gatekeeping; what's that about? One more thing; take that "salt" back to SO where it's accepted in the culture. Here, we're nice. – Harper Sep 20 at 4:35

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