Final answer:
Refrigerant storage cylinders should never be overfilled because the expanding gas could cause the cylinder to burst due to the resistance of liquids and solids to compression.
Step-by-step explanation:
Never overfill refrigerant storage cylinders because tightly constricting the expanding gas is equivalent to compressing it, and both liquids and solids resist being compressed with extremely large forces. If the cylinder is overfilled, the pressure inside the cylinder will increase, potentially exceeding the safe limit and causing the cylinder to burst.