Question

Physical defects to a cylinder can lead to a malfunction or dangerous explosion. How can you determine how much cylinder damage dictates that the extinguisher should be removed from service?

Answer 1

The presence of liquid CO₂ in a fire extinguisher is dependent on the temperature relative to the CO₂'s critical temperature of 31 °C. Below this temperature and under pressure, CO₂ can exist as a liquid, hence the sloshing sound when shaken. Above this temperature, CO₂ cannot be liquefied by pressure and exists only as a gas.

Step-by-step explanation:

On a cool day with a temperature of 18 °C, when a carbon dioxide fire extinguisher is shaken, one can hear the sloshing sound of liquid CO₂ inside the cylinder. This is because the temperature is below the critical temperature of CO₂, which is 304 K or 31 °C. At this point, the CO₂ exists as a liquid due to sufficient pressure inside the cylinder.

However, on a hot summer day where the temperature reaches 35 °C, the sloshing sound is absent. This indicates there is no liquid CO₂ present in the extinguisher. This is because the temperature is above the critical temperature of CO₂, which means no amount of pressure can liquefy the CO₂. Thusly, the CO₂ in the cylinder exists only in the gas state above its critical temperature, even under high pressure.