When should you turn off your engine while delivering compressed gas?

Turning off the engine before unhooking the hoses is important for ensuring safety during the delivery of compressed gas. The primary reason for this is to minimize the risk of ignition or fire. An engine running can produce sparks or heat that may ignite flammable gases if there's a leak or if any gas is accidentally released while disconnecting the hoses.

By turning off the engine first, you reduce the potential hazards associated with handling compressed gas. It's critical to maintain a safe environment while working with such materials and to follow proper procedures to prevent accidents.

In the context of gas delivery, the other choices do not prioritize safety in the same way. For example, running the engine while connecting or unhooking hoses could increase the likelihood of an accident. Hence, turning off the engine before any disconnection is crucial for safe operations in handling compressed gases.