The low air warning system must alert at what air-volume percentage?

• A. 10%
• B. 30%
• C. 40%
• D. 20%

Answer: (D)

Low air warning is about giving a timely alert when the SCBA cylinder’s air is running low, so the wearer has a safe, practical margin to retreat. The standard threshold is about one-fifth of the rated cylinder volume, which is 20 percent. At this point, depending on breathing rate, a firefighter or technician typically has several minutes of air left to exit to fresh air or to complete a controlled retreat, reducing the risk of running out during a critical moment. A warning at a smaller percentage (like 10%) would leave far too little time to react, while a warning at higher percentages (30% or 40%) would trigger earlier than needed and could disrupt operations or create unnecessary urgency. Therefore, the 20% mark provides a balanced, safety-oriented alert.