If he doesn't know anything about it, its probably because he's collecting bottles and bringing them to a welding supply store and exchanging them. That's what my local homebrew place does...I just go directly to the welding gas place and save a buck or two on the homebrew shop's markup...the welding supply place is closer to home anyway.
The bottle certifications are regulated by law, the bottles have to be recertified periodically for safety.
Thanks to everyone helping me. CO2Art complete system and 5lb. tank arriving this week. Aquarium is 46g. and I only have an Aquaclear HOB filter currently. LED is Fluval 3.0. I dose Thrive twice weekly, change about 9g water once a week. Tank is heavily planted with less demanding plants(crypts, anubias, val, dwarf sag,a few small swords, etc.) I am slowly converting to more colorful, higher demanding plants. I added a couple bunches of Reineckii and L. Repens late last week. I will be very cautious with the start of the CO2 to avoid pitfalls ( 1 bubble per sec?). Can anyone give me some startup tips this dummy may not have thought about? I greatly appreciate your help.