Answer :

Final answer:

The maximum travel distance for a Class D fire extinguisher should not exceed 75 feet (22.9 meters). Understanding the critical temperature of carbon dioxide is crucial for the proper function of CO₂ extinguishers, which should not exceed 31.1°C. Exposing extinguishers to high temperatures, like in a closed car, can significantly increase the internal pressure, creating a hazard.

Explanation:

For Class D fires, which involve combustible metals such as magnesium or aluminum, it is important to have the appropriate type of extinguisher available and placed at a safe distance. These types of extinguishers are usually a specific dry powder type tuned to the nature of the combustible metal. OSHA recommends that the maximum travel distance to an extinguisher for Class D fires should not exceed 75 feet (22.9 meters). As for all extinguishers, they must be easily accessible, in working order, and employees should be trained in their use.

Understanding the critical temperature of carbon dioxide is essential when considering the use of CO₂ fire extinguishers. At cooler temperatures, the CO₂ within the cylinder exists as a liquid and a gas in equilibrium. However, at temperatures above the critical temperature of carbon dioxide, which is 31.1°C (87.98°F), this equilibrium cannot exist, and the CO₂ stays in a gaseous state, which is why no liquid is observed on a hot day at 35°C.

When a CO₂ extinguisher is left in a hot environment, such as a closed car in Arizona, the pressure in the extinguisher can rise significantly with the increase in temperature. For example, a fire extinguisher filled with CO₂ to a pressure of 20.0 atm at 21°C can experience an increase in internal pressure when the temperature reaches 71.1°C. It's important to store extinguishers in a controlled temperature environment to prevent such hazards.

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