Carbon dioxide is different from other compressed gasses in several ways... One of the ways is that at Medium-high compressions, the gas will turn to liquid. Don't have the time to look it up... But I think it's something like 700psi.
As CO2 gass is drawn from the bottle, liquid CO2 boils off to keep the pressure in the bottle constant.
So unlike say Argon or Oxygen.. Where a bottle will be filled up to about 2200 psi and as it is used, you can see the pressure decrease...... C02 will keep the same pressure as the liquid boils off the bottom and then when all the liquid is gone, the pressure will quickly drop... (this has caught me with pants down more times than I can count)
All this to say... the C02 has liquid and drawing from it while it is laying horizontally is something I would avoid unless your gas supplier has given you instructions to do it safely. Having a bottle on a cart at an angle a few degrees off of perpendicular is probably going to be ok... But your gas supplier can give you absolute assurance or a black and white answer to each question.
Edit:
Welcome to the forum Bill !
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The IFC (International Fire Code) states that compressed gas containers and cylinders with a capacity greater than 5 L, except those designed for use in a horizontal position, are to be stored in an upright position with the valve end up.
You gave me an idea. I looked up CO2 and discovered that it stays as a gas till about 1400psi at room temp. I noticed that my gas supplier always only fills to about 1400psi. I should mention I'm on the island of Roatan, 40 miles off the Honduran coast and I don't speak Spanish and the gas supplier's English is unintelligible. I take what I can get.
I believe I now know why my 3000psi rated tank is always short filled - to avoid the gas going liquid. I've tried to shake the tank and never felt or heard a liquid sloshing around. As its all gas, I think I can incline it so that it is no higher than the welder.