What is a notable feature of a membrane dryer?

A notable feature of a membrane dryer is that it does not require any consumable supplies or electric power. This makes it efficient and convenient to use since it operates through a passive process of moisture removal rather than relying on electricity or chemical absorbents.

Membrane dryers use semi-permeable membranes to selectively allow water vapor to permeate while retaining larger gas molecules, effectively reducing humidity in the air without needing external resources. This aspect is particularly beneficial in settings where power availability may be limited or where avoiding ongoing costs for consumables (like filters or desiccants) is a priority.

The other features mentioned in the options involve mechanics that may not be inherent to membrane dryers. For example, creating a vacuum for moisture extraction is more characteristic of vacuum desiccators or vacuum dryers rather than membrane types. Similarly, while constant monitoring can be important for various dryer types to ensure efficient operation, membrane dryers typically require less intensive oversight due to their straightforward functioning. Lastly, maintenance costs can vary, but membrane dryers are generally designed to be low-maintenance compared to others that may require regular replacement of mechanical parts or consumables.