FAA Powerplant Written Practice Test

What happens to the allowable pressure range inside a fire extinguisher container as air temperature increases?

1. Decreases

2. Stays the same

3. Goes up

4. Varies unpredictably

The correct answer is: Goes up

As the air temperature increases, the pressure inside a fire extinguisher container also increases. This is due to the relationship between temperature and pressure as described by Gay-Lussac's Law, which states that the pressure of a gas is directly proportional to its absolute temperature when the volume remains constant. In a fire extinguisher, as the temperature rises, the kinetic energy of the gas molecules increases, leading to more frequent and forceful collisions with the walls of the container. This results in an increase in pressure within the extinguisher. Therefore, the allowable pressure range effectively goes up with increasing air temperature, allowing it to safely function in high-temperature environments. This understanding highlights the importance of monitoring temperature conditions for fire extinguishers, as exceeding certain temperatures could lead to dangerously high pressures, risking rupture or failure.