HPA tanks can never be filled with CO2, period on a steel tank you will simply obliterate the regulator if it even allows you to try to fill it that way instead of through the fill nipple. On a carbon fiber tank, you have yourself a bomb if you actually get any CO2 in it. There used to be some carbon fiber CO2 tanks for the original shocker's as they needed larger tanks due to their brutal inefficiency, but that is neither here nor there.
But an hpa tank is designed to store air in a gaseous form at either 3000 or 4500psi. The tank has a regulator built into it to reduce the output to a pressure usable by a paintball marker which is typically less than 850psi. It is a clean and efficient air source, but volumetrically it is less efficient than a CO2 tank of comparable size.
A CO2 tank is either a steel, aluminum, or chromoly tank without a regulator designed to store liquid CO2 at a pressure of right around 8-900 psi. They are in no way similar or compatible.
Your sstatement about antifog tells me you are relatively new to the sport or have never used a high end mask such as a profit, i4, grillz, etc... There is no decent substitute for a dual pane thermal lens. Vforce has a decent coating, but it wears off and boom fog city. Also masks that don't come with decent lenses tend not to be decent masks, so if you are having to buy "anti fog" you went cheap on the mask and have already screwed up.
