When is it acceptable to use spark producing devices in the pumproom with grades A, B, C, and D liquid cargoes?

Using spark-producing devices in the pumproom with grades A, B, C, and D liquid cargoes is appropriate when the compartment itself is gas free. This is because being gas free means that the atmosphere in that compartment does not contain flammable vapors at concentrations that could ignite if a spark were produced.

It is crucial to ensure that the specific area where these devices will be used is free from explosive mixtures. Even if tanks are inerted or empty, there could still be residual vapors that would pose a risk in an improperly ventilated area. Thus, checking that the compartment is gas free ensures the safety of personnel and equipment while working in close proximity to potentially hazardous liquid cargoes.

While other options might seem relevant to safety protocols, they do not guarantee the same level of protection against ignition sources as confirming the gas-free status of the specific compartment where the spark-producing activities will take place.