In response to a question about the internal pressure in a CO2 bottle at a given room temperature, one of our members, MADMAN280
posted this useful information:
Originally Posted by madman280
When a CO2 tank is reasonably full it will contain a mixture
of both CO2 liquid and vapor.
As long as both liquid and vapor are present,
the pressure in the (CO2) tank will depend only on the (ambient) room temperature (not "fullness")
as shown in the table below:
Tank Temperature Cylinder Pressure
The gauge pressure (PSIG) is approximately 14.7 psi less than the values in the table above. The temperature to pressure relationship is logarithmic. Thats why its not a good idea to leave a full cylinder in your trunk on a hot day.