What does the term Off Air mean in the context of the air brake system?

What does the term Off Air mean in the context of the air brake system?

• A. Not being supplied with air pressurized to 60 PSI or more.
• B. Being supplied with air pressurized to 80 PSI.
• C. The brakes are released automatically.
• D. The locomotive is in standby.

Answer: (A)

Off Air means the air brake system is not being supplied with air pressure at or above a baseline release level (60 psi is the common threshold used). In practice, having 60 psi or more keeps the brakes effectively released; when the pressure falls below that point, the system is considered Off Air. So the phrase describes a low-pressure condition in the brake system, not a state where brakes are automatically released or the locomotive is simply in standby.

Off Air means the air brake system is not being supplied with air pressure at or above a baseline release level (60 psi is the common threshold used). In practice, having 60 psi or more keeps the brakes effectively released; when the pressure falls below that point, the system is considered Off Air. So the phrase describes a low-pressure condition in the brake system, not a state where brakes are automatically released or the locomotive is simply in standby.