That made me chortle momentarilyLike .. Empty bottle of Carbon canisters .. That'll be cheaper because there's no compressed air in them .. You can get them in steels lol. Like sometimes for shipping they empty them so they can ship them, then you fill them yourself.
The "weight" of air, is more noticeable in a dive tank, taking the weight of a 12L Steel 4500psi (300 bar) tank from about 19KG down to a piffling 18KG...that's how much 54,000L of air weighs
So in a small 1.1L, my guess is that a full or empty bottle will fit in the same weight category for posting purposes
But as stated, it is against the rules to post a filled bottle...the couriers like to know, that while they are hurling packages across the warehouse, none of them are likely to explode and kill the monkeys that "work" there.
So, bottles, or technically receivers.
Steel ones, as usually used for compressed air on punter sites are heavy and normally only fill to 3000psi.
Fibre wrap bottles, are made with an aluminium bottle, wrapped in carbon kevlar. Much lighter.
Stako bottles, are carbon kevlar as well, but they have a special (some would say potentially hazardous) plastic liner, which makes them extremely light.
Fibre wrap tanks, come in 3000psi (older), 4500 psi and 5000psi flavours, but no site I have been to can fill to 5000psi, so it just means the bottle has a better safety margin, albeit mild.
Fibre wrap bottles are also subject to tighter testing schedules, which varies between newer and older bottles.
Some bottles are DOT tested, which is an American standard and not for use in the UK.
Some bottles are HSE tested, which is the UK standard.
Some bottles are Dual tested, DOT and HSE so they are OK here too.
The latest bottles are CE or Pi marked, which is a European standard, so also OK here too.
Test wise, you have between 3 and 5 years between tests, from the "born" date on the bottle. Some bottles may require 2.5 year tests, alternating between a Hydro test and a visual inspection.
Stako bottles, are single use as such and cannot be tested.
Regarding, "I've got no fecking clue.Lmao." GET A FCUKING CLUE!!!
Don't take offence to that. High pressure air, as has been highlighted recently, can be very hazardous, even for those who are used to using it and think they know the deal, so to have no idea about it, is a bad thing.
You are doing the right thing, by asking questions on here and you will get sound advice, from most people (Tom Allen, Russ Smith etc).
H-PAC, is a company that specialises in all matters of compressed air and often provide compressors etc at large tournaments, they will be happy to answer any questions you have.
Lastly. In case you were mistaken, HPA (compressed air) and N2, are different. N2 is only nitrogen (an inert, "safe" gas) commonly used in America. It's actually cleaner and more consistent that HPA, but only on a physics level and not in the same league as the difference between CO2 and HPA.