Quote Originally Posted by Max
Do fire extinguishers have regulators already fitted? If so what pressure do they regulate it down to and how do they cope with liquid co2?
A CO2 fire extinguisher uses the pressure drop between bottle and open air to freeze the liquid CO2 into a pretty snowcloud. It's how those things work. CO2 attacks 2 sides of the firetriangle. Removes heat and oxygen.

It's also the reason why these have a dip-tube. To draw up the liquid.