Which of the following is not part of proper care for my scuba cylinder?

Keeping some air in a scuba cylinder is not a standard practice for proper care and maintenance. While it’s important to have your tank filled with air before a dive, the proper storage and upkeep involve ensuring the cylinder is not overfilled and maintaining the integrity of the tank when it's not in use.

When a scuba cylinder is stored, it's typically best to leave it either empty or filled to a safe pressure, but not allowing it to remain at high pressure for extended periods without use. Regular full fills should be avoided unless you are actively diving, as this can contribute to wear and potential safety concerns.

The options regarding storing the tank in a cool place, inspecting it regularly for damage, and covering the valve when not in use are all critical components of proper cylinder care. Each of these practices helps preserve the integrity and safety of the equipment, ensuring that the scuba cylinder functions correctly and remains safe for diving activities.