CO2 is an odd gas. If you have ever used a CO2 fire extinguisher you know that what comes out when you open the valve wide open is not a gas, so much as it is a shower of dry ice particles. And a small particle of dry ice is a very, very much smaller volume of CO2 than an equal mass in gaseous form. When you convert any liquid to a gas you have to supply heat to the liquid to make it change to a gas. There is a limit to how fast you can transfer heat to a "puddle" of liquid CO2. So, I suspect that if you knocked the top off of a CO2 bottle, you would first get a gush of dry ice particles, followed by a much slower shower of dry ice particles. (Dry ice because the heat needed to convert the liquid CO2 to gaseous CO2 would have to come largely from the CO2 itselt, which would freeze the gaseous CO2 being ejected.) The real problem is that of any compress gas cylinder - there is a lot of energy stored in the compressed gas, so if it lets go suddenly, the cylinder is a projectile. But, a CO2 cylinder can't be nearly as dangerous as a compressed air cylinder, because the air is still a gas in the cylinder, not a liquid.