Releasing gas from a bottle via Arduino - opening a valve? I'm looking for a mechanical component that enables me to do two things:


contain a gas in a bottle and if opened, the gas should smoothly flow out (with the same pressure as a child blowing out candles on his birthday cake)
a valve for the bottle that can be opened by an Arduino when powered via USB


I already figured out that there are outlets for CO2 capsules. This could work, but then I'd need to figure out a way to decrease the pressure in order to receive a gentle gas flow. 

Do you know any better approaches? Thanks in advance!
If you can tolerate a decreasing flow as the pressure in the bottle drops, a simple restrictor (fluidic equivalent of a resistor) will limit the flow but of course, I = E/R; the flow will be proportional to the bottle pressure. If that is acceptable, it is probably the cheapest, simplest, and most reliable way.