Which of the following can limit air supply during SCBA use?

The most relevant factor that can limit air supply during SCBA (Self-Contained Breathing Apparatus) use is the physical condition of the user. The physical condition encompasses a variety of elements, including the user’s fitness level, respiratory health, and overall stamina. If a user is not physically fit or has underlying health issues, their breathing efficiency may be compromised, leading to quicker exhaustion of the air supply. Additionally, physical exertion can increase the rate of air consumption, reducing the amount of time a user can safely operate with the SCBA before the air supply is depleted.

Other factors may not directly influence the air supply in the same manner. User's knowledge plays a critical role in effective SCBA operation but does not inherently affect the amount of air available. The type of SCBA can impact operational effectiveness, but it does not change the air consumption rate based on individual user physiology. Lastly, the time of day is generally irrelevant to air supply limitations, as it does not affect the SCBA's function or the user's physical condition.