In what type of operation is the use of LPG in liquid form not prohibited?

The use of LPG in liquid form is not prohibited in hot air balloon operations because this application requires the portable nature and specific properties of liquid LPG for efficient combustion and maximum performance. Hot air balloons utilize LPG in its liquid form to achieve rapid heating of the air within the balloon envelope, which is essential for ascending. The design of the burners in hot air balloons is specifically engineered to accommodate liquid LPG, allowing it to vaporize effectively and produce the necessary heat.

In contrast, operations such as cooking appliances and vehicle fueling typically utilize LPG in vapor form for safety and efficiency reasons. Industrial refrigeration systems often rely on propane as a refrigerant, which is handled in a form that differs from direct usage of LPG in its liquid state. The characteristics of LPG in different applications dictate how it can be safely utilized, leading to a clear distinction that hot air balloon operations represent an acceptable use of LPG in its liquid form.