Final Answer:
When delivering compressed gas and running a pump with the engine, it is advisable to turn off the engine before unhooking the hoses after completing the delivery.
Step-by-step explanation:
Turning off the engine before unhooking hoses is a safety measure commonly observed in the handling of compressed gases. When the engine is running, the pump is active, and there is a potential for residual pressure in the hoses. If the hoses are disconnected while the engine is still running, it may lead to the release of compressed gas, posing safety hazards.
By turning off the engine before unhooking the hoses, any remaining pressure in the system can dissipate, reducing the risk of unintended gas release. This practice aligns with safety protocols and helps ensure a secure and controlled environment during and after the delivery of compressed gases.