The type of system your pack should use, either an open system or a closed system, depends on the type of activity you plan to engage in, the climate, and the environment you will be operating in. An open system is characterized by adequate ventilation, allowing air to move freely in and out of the system. Open systems are typically more suitable for warm or hot climates, as they allow for air flow to help regulate body temperature and prevent overheating. They are also generally easier to maintain and lighter in weight compared to closed systems.
On the other hand, closed systems are typically sealed and do not allow air to move in and out. They are better suited for colder environments and activities, as they provide insulation and prevent cold air from entering the system. However, they can be heavy and require more maintenance than open systems. Ultimately, the decision between an open system and a closed system will depend on the specific needs and requirements of the activity and the environment in which it will take place.