LPCO2

I was wondering if anyone had an experience with LPCO2 systems. I've been involved in refrigeration systems for 10 years and I work onboard a ship so its all left up to us to do. We are trained but sometimes do not receive training with up to date systems.

I want to change out a simple pressure switch that runs a refrigeration compressor that cools a LPCO2 tank. I just am a little concerned that when I close the valves to the gauge line, what will happen to that CO2 in the gauge line as its exposed to atmospheric pressure. I have one ball valve for gas or upper gauge line and the other gauge line connects to the bottom of the tank in a liquid. I just suspect some freezing here and just wondering. Thanks.