How long can a typical SCBA provide breathable air under normal conditions?

The correct duration for how long a typical SCBA can provide breathable air under normal conditions is generally in the range of 30 to 60 minutes. This time frame is contingent on multiple factors, including the size of the cylinder, the user's respiratory rate, and the conditions of use.

Most standard SCBA units are designed to offer approximately 30 to 60 minutes of air supply during standard operating scenarios, allowing for effective use in emergencies such as firefighting or other hazardous environments. This range ensures that the user has enough air supply to perform their duties safely while also accounting for possible variations in air consumption based on physical exertion, so typical durations will fall within this range.

The other options suggest either shorter or significantly longer durations than typical SCBA expectations. For instance, while a 10 to 20 minutes range might apply in highly strenuous situations or with small tanks, and 60 to 90 minutes or 2 to 3 hours would exceed the capabilities of standard SCBA, leading to potential misconceptions about the equipment's capabilities. This understanding is vital for ensuring that users can effectively plan their operations and manage their air supply during emergencies.