What feature should not be equipped on medical air receivers?

The correct answer highlights the importance of safety and functionality within medical air receivers. A medical air receiver is designed to store compressed air used in medical applications, ensuring that it meets specific standards for purity and pressure.

Including a temperature indicator is unnecessary because medical air systems primarily rely on pressure readings to manage the system's efficiency and safety. While temperature can be a consideration in certain aspects of compressed air systems, such as monitoring for overheating or potential failure, it does not play a critical role in the operation or safety checks for medical air receivers. Therefore, incorporating a temperature indicator does not add value or enhance safety in these specific medical applications.

On the other hand, features such as sight glasses, automatic and manual drains, and relief valves are essential. A sight glass enables monitoring of the liquid level, ensuring that the receiver operates within safe limits. Automatic and manual drains are crucial for removing accumulated condensate, which can introduce contaminants. Relief valves are vital for preventing overpressurization, protecting the receiver and the connected systems.