What is the main function of the Oxygen storage tanks in the O2N2 Shop?

The main function of the oxygen storage tanks in the O2N2 Shop is to supply oxygen for breathing purposes. These tanks provide a vital resource for personnel who require a source of breathable oxygen, particularly in scenarios where environmental conditions may not be safe or sufficient for safe respiration. The tanks are specifically designed to store oxygen in a manner that ensures it can be readily accessed and used by submarines or other vessels' crews, especially during operations where the air quality may be compromised or when working in confined spaces. This ensures the safety and operational capability of the crew in various environments.

The other options, while related to gas storage and supply, do not accurately describe the primary purpose of the oxygen tanks as being focused on providing breathable oxygen, highlighting the specific function they serve in ensuring crew safety and operational readiness.