What is the outer shell of firefighter gear constructed from?

The outer shell of firefighter gear is constructed from flame-resistant and water-repellent material to provide the highest level of protection against the extreme conditions faced during firefighting operations. This choice is correct because the materials, such as Kevlar, Nomex, or other specialized fabrics, are designed to withstand high temperatures, resist ignition, and protect against heat and steam, while also resisting water to keep the firefighter dry. The ability of these materials to withstand flames and protect the wearer from heat is crucial during a fire emergency, ensuring the safety and effectiveness of firefighters as they perform their duties.

In contrast, options like plastic and rubber, cotton blends, or aluminum and steel do not provide the necessary combination of heat resistance and flexibility that modern firefighting gear requires. While they may have their uses in various applications, they lack the specific protective qualities essential for the safety of firefighters in active fire scenarios.