When purging, one should avoid applying a vacuum to containers that may have contained?

When purging, it's essential to avoid applying a vacuum to containers that may have contained propane because propane is a flammable gas that can create a dangerous situation. Applying a vacuum to a container that holds residual propane could lead to the rapid evaporation of the gas, potentially resulting in an explosive atmosphere if ignition occurs. Propane is also heavier than air, which means that in a confined space, it can accumulate at low levels, creating a risk of fire or explosion.

Additionally, the characteristics of propane as a liquefied gas under pressure make it particularly hazardous when vacuums are involved. If there are any leaks or residual gas, the vacuum can exacerbate the problem by drawing in air or creating a spark that could ignite the propane. Therefore, safety protocols strongly advise against vacuuming containers that may have housed any flammable substance, especially gas like propane. This highlights the importance of safety and proper handling of potentially hazardous materials in processes involving purging.