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RE: Grades of CO2

Richard Rajski asked about the differences between different "grades" of

> I have the opportunity to buy an ex-brewery carbon dioxide
> cylinder at very
> reasonable cost. The company supplying it has told me they can
> only fill it
> with industrial grade CO2 and not food grade. They were however unable to
> give me any information as to the level of impurities in each.
> Does anyone know ? Is industrial grade OK to use on an aquarium ?

BOC Gases has a chart on their web site
tm] which lists the various grades of CO2 that THEY supply, and the impurity
levels and makeup of each grade.  This might give you an idea of the sorts
of things that could be in CO2 of different grades.

CO2 is available in a wide range of "types" - make sure that what they are
selling you is PURE CO2 and not "CO2 in air", or another gas. There are many
industries which use specific mixtures of gases for specific uses - I doubt
that there is any one "industrial" grade. See
aprot.htm] for some of the EPA Protocol possibilities.

If you inadvertantly buy a gas "mixture" rather than the pure CO2 gas, you
could be asking for trouble. Personally, I would never buy something like
CO2 from a source that could not or would not give me the details to exactly
WHAT they were selling (in your case, I would expect your dealer to explain
exactly the differences between the two grades "industrial" and "food" and
if he only sells "industrial" he SHOULD know the allowable levels of
impurities for that grade. If he doesn't know (or more likely, can't be
bothered to look the information up for you, if he doesn't know it off the
top of his head), he's a doofus who doesn't deserve your business.

Pure CO2, from a reputable company which will stand behind their product is
very inexpensive. There is absolutely no need to deal with companies which
can't, or worse won't, answer your legitimate questions.

James Purchase