A bad day with CO2...

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.  :)
vandi at well_com