Panels and grilles that require removal for servicing of decorative appliances must not be what?

The correct answer is that panels and grilles requiring removal for servicing of decorative appliances must not be attached. This is because if they are permanently attached, it would impede access to the appliance for maintenance and service. For safety and functionality, it is important that these components can be easily removed without the need for tools or significant effort.

In the context of servicing appliances, accessibility is critical. If panels and grilles are attached, it can lead to complications, requiring additional time and effort to remove them for maintenance. This goes against the design principle that emphasizes efficient and safe access to components that need regular servicing or inspection.

The other options — being fixed, closed, or hinged — do not inherently prevent easy access. A hinged panel, for example, may provide quick access while being secured when closed, and a closed panel can still be removable if designed appropriately. Therefore, the focus on attachment as a barrier to servicing highlights the need for removable components in the design of decorative appliances.