What is a critical step before fueling any vehicle at the station?

Shutting off the vehicle's engine before fueling is essential for several safety reasons. When a vehicle is running, it can produce sparks, heat, or other sources of ignition that could ignite fuel vapors, leading to potentially hazardous situations like fires or explosions. By ensuring the engine is turned off, you greatly reduce the risk of ignition and create a safer environment for refueling.

In addition to being a safety precaution, turning off the engine is often a requirement at many fueling stations to comply with safety regulations. This practice not only protects the individual fueling the vehicle but also safeguards other customers and station personnel.

The other actions mentioned do not promote safety during the fueling process. For instance, leaving the engine running increases the risk of ignition, while having smoke or flames present directly contradicts the fundamental safety requirements at any fueling station. Moreover, attaching the nozzle before ensuring proper safety measures could lead to dangerous situations, emphasizing the importance of prioritizing safety protocols like shutting off the engine.