Smaller cylinders can be used. You'll have to change the cylinders more often 
of course, which means more days spent waiting for reference gas values to 
stabilize as the old gas gets worked out of the system. It's consumed slowly, 
which means it takes awhile. A valve to bleed the line with cylinder changes 
would be useful as the old ref. gas would be replaced very slowly with the new 
one otherwise.

On Monday 29 March 2010 11:45:39 am you wrote:
> Hi All,
> 
> In a recent reply to a question regarding the location of a new stable
>  isotope lab, Wolfram Meier-Augenstein mentioned the need to store any
>  pressurized gas cylinder supplying CO2 for reference gas purposes at
>  constant temperature (i.e. ideally within the lab). I presume that similar
>  issues arise where any other liquified gas is used as a reference; in this
>  case I'm thinking of N2O. Could someone with the requisite experience
>  confirm that any cylinder of N2O used as a source of reference gas should
>  also be stored inside the lab, and NOT outside in a conventional external
>  cylinder storage area?
> 
> Whilst on this subject (and assuming that both N2O and CO2 do need to be
>  stored in the lab), in order to minimise potential health and safety
>  concerns I'm thinking of using relatively small cylinders of CO2 and N2O.
>  It is possible for me to obtain both gases in 50 litre volumes (at 21 bars
>  cylinder pressure) that will fit conveniently out of the way under a
>  bench. Can anyone see any problems with this approach (as opposed to
>  buying more conventional large cylinders containing 2000 litres)?
>  Obviously the cylinders would need to be changed more frequently, but are
>  there any other issues that I need to consider?
> 
> Regards,
> 
> Steve Crowley
> 
> Department of Earth & Ocean Sciences
> University of Liverpool
> 4 Brownlow Street
> Liverpool
> L69 3GP
> UK
> 
> 0151 794 5163/5164
> 
> ____________________
>