Can you fill up a co2 tank withan air compressor?

yes you can when you use a compressor only fill up the co2 tank for 2 seconds for every ounce the tank can hold (9 ounce tank=18 seconds)

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However, the CO2 tank is designed for CO2, not ordinary air, and it is rated for only a specific pressure. If you don't have the proper equipment to do this, it is better for your own safety to leave it to a professional.