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CO2 Cylinder Dangers


  1. CO2 safety
    by Earle Hamilton <> (Tue, 11 Jul 1995)
  2. Yeast explosion: Volume of CO2
    by David Brockman Wheeler <dwheeler-at-leland.Stanford.EDU> (Wed, 19 Jul 1995)
  3. A bad day with CO2...
    by Mike Bateman <> (Thu, 1 Feb 1996)
  4. Aquatic Plants Digest V2 #521
    by Edziu Iskra <> (Sat, 15 Feb 1997)
  5. Compressed bottle
    by "Simone e Pierluigi Vicini" <psvicini/> (Tue, 6 Jan 1998)
  6. Dead SAEs
    by George Booth <booth/> (Wed, 12 Aug 1998)
  7. dangers of a pressurized gas cylinder?
    by "Frank I. Reiter" <FIR/> (Thu, 10 Dec 1998)
  8. dangers of a pressurized gas cylinder?
    by Zxcvbob/ (Fri, 11 Dec 1998)
  9. Aquatic Plants Digest V3 #1042
    by George Slusarczuk <yurko/> (Fri, 21 May 1999)
  10. Nearly asphyxiated by CO2
    by Loh Kwek Leong <timebomb/> (Fri, 3 Nov 2000)
  11. Cat instigated problem
    by "alex pastor" <alexp/> (Sun, 18 Mar 2001)
  12. An error!
    by Warren Wu <WarrenWu/> (Sat, 5 Jan 2002)

CO2 safety

by Earle Hamilton <>
Date: Tue, 11 Jul 1995

Dave Webb's post re problem of exploding DIY yeast/syrup mix
was so funny I almost fell of the chair laughing. I'm sure
Dave was not laughing when he had to clean up the mess.  Pressure 
generated by fermentation has caused more than one explosion in the night 
for amateur alchohol produers.  Just how you would vent a DIY unit 
without loosing needed pressure to drive the co2 into the water is beyond 
my creative powers.  Perhaps somebody can solve the problem.

My real reason for posting is another co2 problem.  For me it was a 
disaster but you may find it amusing and hopefully we can all learn from 
my experience.  My co2 20# tank ran out so I took it to the local 
supplier and got a new tank.  It was last February and the temperature in 
the van was around 60.  I propped the tank on the passenger side and took 
off with the heater on high.  After driving about 15 of the 30 mile trip 
I had just turned off the highway onto a city street going about 25 mph 
when all of a sudden an explosion occurred.  The van was instantly filled 
with fog.  The safety valve released on the co2 tank which dumps the 
entire contents.  I could neither see nor breathe but I sure could 
panic.  I got the van stopped and jumped out gasping for breath.  Then I 
realized I hadn't put it in park so I had to chase it down the street.  
Got it stopped and parked with the tank still going.  I was shaking 
pretty bad and realized how lucky I was not to have had it go off while 
doing 55 on the highway.  Drove back and got another tank.  This one was 
put in the back of the van.
Moral: when transporting any tank of gas the 3000 psi makes it a 
potential disaster. If you have a car, put it in the trunk.  Never let 
the tank get hot by leaving in a closed car.  

Yeast explosion: Volume of CO2

by David Brockman Wheeler <dwheeler-at-leland.Stanford.EDU>
Date: Wed, 19 Jul 1995

Hoa wrote:

>Does anyone know how much volume the 5lbs of CO2 will occupy at atmospheric

Simple: 1 mol/44g CO2 * 2200 g/lb * 5 lb * 22.4 L/mol = 5.6E3 L 
>I wonder if the scenerio above happened while the windows were
>closed, would it suffocate people in a small house or apartment?

Harder: 750 ft^2 * 8 ft ceiling = 6000 ft^3 * 7.5 US gal/ft^3 = 4.5E4 gal
        4.5E4 gal * 3.79 L/gal = 1.7E5 L
   now if all the CO2 escapes into this volume:
        5.6E3 L/1.7E5 L * 100% = 3.2% (v/v)
   In North America the ambient CO2 is ~0.03% (v/v) and so is negligible.
According to the Merck Index, 11th Ed., "Humans cannot breathe air contg
   more than 10% CO2 without losing conciousness." Thus, 5 lb should not
   be dangerous, but you would not want to expose skin, eyes or mucous
   membranes to the escaping gas until it has been diluted by the house's
   air to avoid acid burns.

David B. Wheeler
MD/PhD 4/8 Neurosciences
Stanford University

disclaimer: the above is not official medical opinion nor should these
            opinions be used to justify idiotic behavior or I will
            disavow any knowledge of the aforementioned non-medical

A bad day with CO2...

by Mike Bateman <>
Date: Thu, 1 Feb 1996

I just had an interesting experience with CO2 this week.
I came home one evening to find all six cats acting very odd.  Freaked
out is a better word.  None of them would enter the living room.  I
didn't think anything about it.  Sometimes one of them gets a wild hair
and decides to terrorize the house.
Later that night I opened up the aquarium cabinet to top off the water
in the sump and I noticed a plastic cup, that I keep in the stand to
hold waste test water, was tipped over.  Luckily there was nothing in it
at the time but I thought that was odd.  At first I figured one of the
cats had learned to open the door to the cabinet.  Nah.
I had just had a spare 5 pound CO2 cylinder filled earlier that day and
had stuck it under the aquarium.  It was cold and covered in frozen soap
water (the guys check it for leaks everytime I get it filled).  I looked
and there was a huge puddle of water under the cylinder.  I thought that
was odd.  A newly filled cylinder generally sweats but not THAT bad.  I
proceded to wipe up the mess and lifted the cylinder out to wipe under
it and noticed the cylinder didn't weigh anything.  IT WAS EMPTY!
Suddenly the mystery of the puddle of water AND the freaked out cats was
solved. The 5 pound cylinder had blown its safety valve while I was out.
I figured it must have been pretty loud.
Well I took the cylinder back to the shop and they replaced the safety
valve, which I was suprised to find was only a metal membrane calibrated
to give at 2000psi.  They must have overfilled the tank.  All they do is
set the cylinder on a big scale, zero it, and fill it to 5 pounds with a
little extra to account for the weight of the hose.  It's all very
scientific. :/
I brought the CO2 tank home.  It was time to do a little maintenance on
the aquarium anyway so I sat the CO2 tank off to the side and proceded
to work on the aquarium.  I was just about done and was cleaning up my
mess when my life flashed before my eyes!  The loudest most frightening
sound suddenly sent every cat on a light-speed dash to the basement and
sent my heart pounding out of my chest.  It took about 2 or 3 seconds
for me to regain my composure and to realize what had happened.  The CO2
tank was lying on its side hissing up an eardrum peircing storm.  The
safety valve had blown again, only this time only inches away from me!
Needless to say it took a good hour for my adrenaline levels to
normalize.  It took a little longer for the cats to calm down.  They
were all discussing new living accomodations.
It only took about 45 seconds for 5 pounds of liquid CO2 to escape into
the air.  There was a nice white frozen spot on the carpet.  I didn't
think too much about the additional CO2 in the air as I didn't notice
anything such as increased resperation or light headedness.  There was
plenty of O2 in the air.  I'm sure the house plants LOVED it. :)
A casual glimps at my pH controller revealed something odd though.  My
tank pH had dropped four tenths of a point!  I checked the other
aquarium and it also had dropped an equivalent amount.  The additional
CO2 in the air had caused the aquarium pH to drop!  It took over an hour
for the pH to even start dropping!  It was probably 3 hours before the
pH in the 45g tank returned to normal.  The 75g has a trickle filter so
the pH returned to normal a little more quickly.
I returned the 5# cylinder and they again replaced the safety valve.
This time I had them skip adding that "little extra". I immediately
pulled the 10# cylinder off and placed the regulator on the 5# so that I
could actually SEE the pressure in the tank.  It was only 500psi.  As
the cylinder warmed the pressure rose but stopped at 900psi.  Whew...
So BE CAREFUL out there folks!  I've had these things refilled several
times and this was the first time this has happened.  I hope it'll be
the last!
Oh, I didn't mention that the safety valve had been pointing towards a
large palm plant when it blew.  It blew about a 3" of soil out of the
pot.  That soil covered EVERYTHING within a 12ft radius.  Boy, did I
have a big mess to clean up.  :)

Aquatic Plants Digest V2 #521

by Edziu Iskra <>
Date: Sat, 15 Feb 1997

There's been a fair amount of talk on the list about the potential for
explosion using certain fertilizer ingredients, and some warnings about
DIY CO2 canisters exploding from pressure.  Yet I've never seen a warning
about high-pressure CO2 tanks.  So I'm filling that void.

I don't want to scare anyone, but this is a true story.  At my Alma
Matter, NJIT, we used to call the large gas cylinders used in the labs
"photon torpedoes" because of an incident.  A grad student moved some
cylinders, but failed to use the safety straps to secure the tops of the
cylinders to the harness at the top of the lab table.  After a hose was
tugged, the cylinder fell over, and is it did, the main valve struck some
equipment and was broken.  Because of the pressure inside, the valving cam
right off, and the tank took off.  And I mean OFF.  It went right down the
aisle in the lab, and gathered enough momentum to go THROUGH THE WALL and
into a professor's car.  As I recall, the gas was nitrogen, but it might
have been helium.

Anyway, secure your tanks.  Accidents like these are very, very rare.  The
smaller tanks used by aquarists may not even be large and heavy enough to
damamge themselves when they fall over, but caution is certainly
warranted.  Oh, and if the valve does come open full blast, and even the
tank tank doesn't come off, open a window quick.  Although the gas may not
harm you directly, it WILL quickly displace all or most of the air in the
room, and you may pass out from lack of oxygen.

Sorry, had all this drilled into me in college. . .

Compressed bottle

by "Simone e Pierluigi Vicini" <psvicini/>
Date: Tue, 6 Jan 1998

So my compressed bottle did its job, it emptied last night and now my PH is
less than 5.5 my fish all dead my plants suffering, CO2 level at more than
500 mg/l.
1 KG of liquid carbon dioxide poisoned everything.
That was because of that not working needle valve. 
I hope I will have the patience to start again with my aquarium 

I had to tell you that, I'm mad about that
Simone Vicini (

Dead SAEs

by George Booth <booth/>
Date: Wed, 12 Aug 1998

A counter example may be appropriate here. 

Some time ago we had a "CO2 disastor" when a pH electrode went belly-up 
overnight causing the CO2 controller to think the pH was too high, causing the 
CO2 to be on all night, causing a CO2 level that was close to 140 ppm in the 

All the fish in the 120 gallon tank were in serious shape when we found them in 
the morning. We changed half the water (and the electrode) and hoped for the 
best. We lost 8 adult Rainbowfish out of 12 (Glossolepsis seemed less affected) 
but the adult SAEs, Farlowellas, Corys and Plecos all recovered with no obvious 
ill affects. 

George Booth in Ft. Collins, Colorado

dangers of a pressurized gas cylinder?

by "Frank I. Reiter" <FIR/>
Date: Thu, 10 Dec 1998

> From:
> Excuse me, but I worked with pressurized gas cylinders for 12 years in the
> military.  They pounded every safety rule there ever was into our head from
> "duck when the enemy is firing" to "keep your thumb out from under a moving
> hammer".  They never mentioned to the best of my knowledge any danger
> associated with horizontal storage except the possibility of it launching
> itself when you break the valve off.  If it is stored safely in the tank
> cabinet, what is the likelyhood of that?  Is there some other
> problem you are
> refering to?

If you have watched the input pressure to your regulator over time you may
have noticed that the pressure in your tank stays constant until it is nearly
empty.  The reason for this is that CO2 is bottled at a pressure which keeps
it in liquid form  When a little CO2 is used from the bottle the pressure
drops and liquid CO2 turns to gas until the equilibrium pressure is reached

If your bottle is not vertical you run the risk of forcing liquid CO2 into the

All of the above applies equally to pressurized oxygen and acetylene as well
btw, though the equilibrium pressure is different for each.

- -----
The very act of seeking sets something in motion to meet us;
something in the universe, or in the unconscious responds as if
to an invitation.  - Jean Shinoda Bolen

dangers of a pressurized gas cylinder?

by Zxcvbob/
Date: Fri, 11 Dec 1998

Frank sez:
> If your bottle is not vertical you run the risk of forcing liquid CO2 into 
> the regulator.
>  All of the above applies equally to pressurized oxygen and acetylene as
>  btw, though the equilibrium pressure is different for each.

Your statement about liquid CO2 is true at normal roon temperatures.  It is
certainly not good to have liquid CO2 in the regulator, but at the flow rates
we are using, it may not be *that* bad unless it can attack the diaphram.  I
won't argue either way on this point.  I personally would only use a CO2 tank
in the upright position.

I don't remember the triple point for oxygen, but at normal temperatures, all
the O2 in the tank is a gas and it doesn't matter if the tank is upright,
sideways, or upside-down.  Acetylene is stored under high pressure disolved in
acetone.  If you use an acetylene tank on its side, you will get acetone in
your regulator and hose; and it's also bad for the tank.  That's also why you
have to limit the flow rate from an acetylene tank to 1/7 the capacity of the
tank (I don't remember the exact details here) so you don't force acetone out
of the tank.  You can store an acetylene tank on its side, but then you have
to let it rest for a half hour before using it once you tip it upright.

best regards,

Aquatic Plants Digest V3 #1042

by George Slusarczuk <yurko/>
Date: Fri, 21 May 1999

Hello Hoa,

Your pH swing theory is plausible, but because Dyniar found his dead
fish in the morning, the plants could not have been producing oxygen
without lights. Thus the CO2 "poisoning" hypothesis can not be rejected

I do not know whether CO2 has the same physiological effect on fish as
on mammals, but at higher concentrations it acts in mammals as a

While CO2 will not displace O2 in water, at a certain concentration it
will "stick" to haemoglobin and prevent oxygen/carbon dioxide exchange
in the gills.



> Date: Thu, 20 May 1999 13:22:51 -0700
> From: Hoa Nguyen <>
> Subject: Re: DIY CO2 and asphyxiated fish
> >Date: Thu, 20 May 1999 09:33:53 -0400
> >From: "Dinyar Lalkaka" <>
> >Subject: DIY CO2 and asphyxiated fish
> >
> >The first concrete results of my DIY CO2 experiment were visible this
> >morning: four dead Debauwi cats (Eutropiellus buffei). Their mouths were
> >wide open in the piscine version of Munch's "The Scream." pH was down to
> >5.5. The other fish in the tank were also obviously in distress. A costly
> >experiment. I think that from now on I will leave the spray bar just above
> >water level and let it create better aeration, even if that allows most of
> >the CO2 to escape. Healthy plants are nice but healthy fish are nicer.
> >
> >Dinyar
> Dinyar,
> I don't know if by asphyxiated you meant the fish died from lack of
> O2.  That is not the case.  CO2 does not displace O2 in water as it does in
> air.  If anything, the O2 content should go up with additional CO2, because
> of additional photosynthesis by the plants.  Your fish died from the pH
> swing.  If your water was better buffered (higher KH), then you could pump
> in more CO2, and both fish and plants would be happy.  The key is to
> monitor your pH well initially until you know how much or how fast to
> inject CO2.
> Hoa

Nearly asphyxiated by CO2

by Loh Kwek Leong <timebomb/>
Date: Fri, 3 Nov 2000

Hi, folks,

Reading about Jeff's experience when his fish died because of some problems
with his CO2 system, I like to tell you folks about mine.  Fish dying is a
sad thing but yours truly nearly lost his life because of a gas cylinder.

It happened a few days ago.  My friend, Edward and I were driving home from
the gas company after refilling 7 gas cylinders with CO2.  Only one of the
cylinders was mine, the rest belong to a fish shop where Edward used to
help out.  The gas tanks were lying on the floor of the back seat
compartment.  I know, we should have put them inside the boot but Edward
has a lot of junk inside his boot and it was just too much trouble to
unload them to make space for the gas tanks.

It was just another sunny day afternoon in Singapore.  It was scorching, as
usual.  Edward was driving and I was sitting beside him.  We were just
chatting away when suddenly there was a loud bang like a gunshot and next
thing you know, the whole car was filled with very thick white smoke.  It
all happened in micro-seconds.  I couldn't see a thing and also couldn't
breathe.  The first thought that occurred to me was to wind down the
windows but Edward's car windows were permanently jammed in the close
position.  His is an old car which would have been sent to the scrap yard
long ago if not for the fact that cars here in Singapore are so expensive.

After struggling for what seemed like an eternity, I finally managed to
open up the car door.  The air immediately cleared and I started to breathe
again.  Imagine all that happened while we were driving on the high speed
lane inside a tunnel which is part of an expressway.  I turned to look at
Edward and he was real cool, one hand on the steering wheel and the other
holding his door open.  He told me afterwards that when visibility dropped
to zero, his first reaction was to take his foot off the accelerator.
Fortunately for the both of us, he had the good sense not to slam his
brakes which would be the usual reaction of any driver when he couldn't see
where his car was going.  Although he couldn't see a thing, Edward held the
steering wheel steady which kept the car going on the same lane.
Otherwise, we would have probably either have gone off the road or went
into another lane.  Either way, it would have resulted in a nasty accident.

We stopped on the side after a while to take a look at what happened.  One
of the gas tanks was all frosted over.  It had dumped 5 kilograms of CO2
inside the car in a few seconds.  Edward said it happened probably because
of a sudden change in temperature.  His car's air-conditioning wasn't
really working well and the sudden rise in temperature must have caused the
emergency valve in the gas tank to give way.

Well, thank goodness, I'm still alive to talk about this.  I don't know how
it's like over in the US of A but those few Singapore subscribers who are
reading this should take note that you should never put a fully-filled CO2
gas tank inside your car.  Put it inside the boot and make sure your car
windows are wound down when you are on your way home from the gas company.

Loh K L

Cat instigated problem

by "alex pastor" <alexp/>
Date: Sun, 18 Mar 2001

A number of months ago, my cat decided that he had to indicate to me in no
uncertain terms that he was not happy with what he considered to be neglect
of himself.  He chewed up the CO2 hose.

I thought I'd spliced out the damaged portion but it turned out that there
were two more holes and the CO2 was escaping thata way.

Meanwhile my pH monitor needed a new electrode and I had lots of other 'life
situations' to deal with so the tank was not right up there as a priority.

So the pH went up and the clown loaches altered their behaviour.  For years
they were nice guys leaving the plants alone.   Now, they literally tore the
tank apart.  Leaves floating everywhere, other leaves looking like Swiss
cheese.  Considering how this tank looked a year ago, to look at it now is
to weep+ACE-

Finally I got my act together and started with replacing the CO2 hose,
calibrating the pH monitor, and adding correct amounts of PMDD to the change
water.  The first thing I noticed was that the Clown Loaches no longer
attacked the plants.  Has anyone else seen such behavioural change?

Next, the duckweed and Salvinia started to grow back with a vengeance.  The
plants that survived carnage started to put out new leaves.   Cryptocoryne
which had been chewed down to the 'disappearance' level started to grow new
leaves from the gravel.

However, there developed over the CO2 deprived time a type of brush algae.
I guess it's red because I can rub it off leaves etc. with my fingers.
Today I purchased 4 baby real Siamese Algae eaters.  What bliss+ACE-  This furry
stuff appears to be their 'algae of choice'.  Rocks look as though they'd
been barbered+ACE-

Now for the mystery:  The Jungle Vals are no longer.  They are rather
mini-Vals these days and don't seem to be interested in developing back to
their former glory.  (Mixed blessing in a way.)  Is it possible that the
Cryptocoryne have exuded some type of allelopathic chemical substance into
the substrate that is causing the Vallisneria to be dwarfed?

Also, my pH from the tap is 7.8,  KH 4. (maybe 4.5)  If I lower the pH to
6.8, the fish are puffing in the a.m.  If I increase surface movement to
increase O2 levels, the pH goes up because the CO2 is bleeding off.  Is this
because there aren't enough plants as yet to provide sufficent O2?

Gabriella Kadar
p.s. anyone want a cat who gains oral satisfaction through destruction of
various cords, cables and hoses?  He's smart.  Never chews live wires or
ones with max. voltage running through them.  :)

An error!

by Warren Wu <WarrenWu/>
Date: Sat, 5 Jan 2002
To: erik/

Just writing to let you know that in the July 19th,
1995 post from David
there is an error regarding the calculations for CO2
concentration. It shows in the first calculation a
conversion factor of "2200g/lb". The correct figure is
454 g/lb. Recomputing, the total volume of CO2 gas
comes to 1156 liters, resulting in a dispersed
concentration of .68% (v/v), giving a safety factor of
close to fifteen times.

Hope you all feel a lot better about your CO2 tanks.

Warren Wu   |   KC0HAK

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This page was last updated 17 February 2002