What is the storage pressure of a low‑pressure CO2 system at controlled temperature of 0°F?

• A. 250 psi at 0°F
• B. 300 psi at 0°F
• C. 350 psi at 0°F
• D. 400 psi at 0°F

Answer: (B)

Storage pressure is determined by the saturated vapor pressure of CO2 at the storage temperature. At 0°F (-18°C), CO2’s saturated vapor pressure is about 300 psi, so a low‑pressure CO2 system is designed to store roughly 300 psi. This creates the liquid–gas balance inside the vessel needed for a proper, rapid discharge as a dense gas. If the temperature were higher, the pressure would rise above 300 psi; if lower, it would drop. The other pressures don’t match CO2’s vapor pressure at 0°F, so 300 psi is the correct value.