What is the idle minimum safe distance from an intake and from an exhaust?

• A. Idle: 9 ft from intake; 115-155 ft from exhaust
• B. Idle: 25 ft from intake; 325-725 ft from exhaust
• C. Idle: 9 ft from intake; 325-725 ft from exhaust
• D. Idle: 25 ft from intake; 850-925 ft from exhaust

Answer: (A)

At idle, the hazards come from two different engine effects: ingestion risk at the intake and jet blast from the exhaust. The intake can pull in loose items or clothing, so you need enough distance to prevent anything from being sucked in as the engine breathes. Nine feet provides a practical separation that reduces ingestion risk without being overly restrictive.

From the exhaust, even at idle there is still a blast of hot gas and potential debris being blown outward. A larger clearance is required to avoid exposure to that blast and heat, and about 115 to 155 feet is the range that safely accommodates idle jet blast.

The other options mix distances that don’t match these distinct hazards: some underestimate the ingestion clearance, and others push the exhaust clearance far beyond what’s needed at idle, making them inconsistent with standard idle safety practices.