While unloading Division 2.1 flammable gas, the engine operates the transfer pump and the hose has no discharge-end shutoff valve. When must you stop the engine?
Correct answer: C – After transfer ends but before disconnecting the hose
The engine may run during the transfer when it is needed to operate the vehicle’s pump. After the loading or unloading operation is finished, the engine must be stopped while the connections are disconnected if the hose lacks a shutoff valve at its discharge end. The hose should not be disconnected while the pump remains powered.
Source: Alabama Commercial Driver License Manual — § 9.5.4, “Compressed Gas.”, 49 CFR § 177.840(d) — Class 2 (gases) materials.

