When loading flammable liquids, under what condition is it permissible to leave the engine running?

When loading flammable liquids, it is permissible to leave the engine running specifically when it is necessary to operate equipment such as a pump. This scenario is crucial in the handling of flammable liquids, as having the engine running in this context is essential for the safe and efficient transfer of the liquid. Pumps are commonly used to facilitate the loading process, and if they require the engine's power to function, it is standard practice to keep the engine running during that operation.

In contrast, other scenarios like leaving the engine running solely because of weather conditions or based on a supervisor's directive without regard to operational necessity do not generally justify this practice. While an air conditioning system may be necessary for comfort, it does not pertain directly to safety protocols or operational requirements related to hazardous materials. Safety protocols emphasize minimizing ignition sources around flammable liquids, and understanding this context is vital for personnel involved in hazmat operations.