I did a costume like that, I used CO2 cartridges to inflate a balloon. The whole effect and how we did it is recorded here. scroll down for a breakdown of how it all went together.
I had a harness that held the CO2 strapped to my leg, I needed to use steel reinforced hoses to keep the pressure from blowing the connections. I had a switch at my waist, I plugged in the CO2, it went under pressure, when I hit the switch it discharged into the balloon.
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I had a harness that held the CO2 strapped to my leg, I needed to use steel reinforced hoses to keep the pressure from blowing the connections. I had a switch at my waist, I plugged in the CO2, it went under pressure, when I hit the switch it discharged into the balloon.