🔍 Key Concepts

• CO₂ extinguisher pressure behavior at room temperature (is it driven more by amount of liquid CO₂ or by temperature? ) • Relationship between extinguisher pressure gauge and remaining charge for liquefied compressed gases like CO₂ • Typical service/charging pressure range for portable CO₂ extinguishers at room temperature

💭 Think About

• Think about whether the internal pressure of a CO₂ extinguisher at normal room temperature drops in direct proportion to the amount of CO₂ discharged or stays roughly the same until almost empty. • Consider what creates the pressure inside a CO₂ extinguisher: is it a separate compressed gas, or the vapor pressure of the CO₂ itself above the liquid? • Compare the answer choices: which look more like full CO₂ cylinder pressures at room temperature, and which seem too low or too high for a partially used but still partly liquid-filled cylinder?

✅ Before You Answer

• Verify how liquefied gas (CO₂) pressure behaves: does 50% loss of charge mean 50% loss of pressure? • Recall approximate vapor pressure of CO₂ at room temperature and whether that is closer to tens, hundreds, or nearly a thousand PSI. • Check which pressures are more typical of empty vs. full CO₂ fire extinguishers at about 70°F (21°C).