What is pressurized to 4500 psi?

The correct choice, which is the Self-Contained Breathing Apparatus (SCBA), utilizes high-pressure tanks to store the air that is supplied to the user. Typically, SCBAs are pressurized to around 4500 psi to ensure that a sufficient amount of breathable air can be stored in a compact tank. This high pressure allows for a longer duration of use and ensures that first responders have adequate air supply in environments where oxygen may be limited or contaminated.

In contrast, other options do not typically operate at such high pressures. High-pressure fire hoses are designed to handle significant water pressures but do not reach the same levels as SCBA tanks. Emergency air compressors operate to refill these tanks but do not maintain 4500 psi themselves. Water mist systems function to control fire through water dispersion and are not associated with maintaining high pressure in the same context as SCBA. Understanding these distinctions is crucial for comprehending the specifications and operational capacities of different equipment utilized in emergency scenarios.