On Mon, 29 May 2000 12:31:09 +0300, Manos Manoli wrote:

>I have talk with my Gas supplier and a found out that 99.995 purity on
>He costs a fraction (100$)
>comparing to the 99.999=A0 (400$) that im=A0 buying up to now. The main=

>point is that they cannot
>certify the impurity. That means that they cannot tell you whats in the=

>rest of 0.005.
>So i figured that if the rest is O2 or Co2 then there is not really a
>problem but what if the
>rest is Co ?? I talk with a friend and he suggested to use 2 on line
>filters a Sub micron filter for
>the particles and a catalyst filter to break Co to Co2 .
>
>Should i spend the 600$$ for the filters or should i just take my
>chances with 99.995 ?
>
>Manos

Manos, what you need to do is request gas analysis sheets from your
supplier (and others in your area).  These should contain information
regarding the highest permissible levels of hydrocarbons, CO, H20,
etc., for a given grade of gas.  Once you have that information, you
can determine how pure you need it, since even 99.9 will do if the
other 0.1 is harmless.  Generally, USP grade oxygen and USP helium is
what is best suited to diving.  Order USP by name, or ABO (aviators
breathing oxygen), which is the same thing but certified to a lower
moisture content.  Once you get into research grades (specified by
number of nines following the decimal point), things get expensive
quick.

-Sean


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