Which of the following is NOT considered a listed device?

A device that is considered "listed" is one that has been tested and evaluated by a recognized testing agency, such as Underwriters Laboratories (UL) or Factory Mutual (FM), according to established standards. This process ensures that the device meets specific performance criteria and safety standards, which is essential in the context of fire protection systems.

Looking at the options, the choice that is not considered a listed device relates to the general nature of the fire protection component mentioned. While it may be used widely in residential areas, this does not inherently indicate that it has undergone testing or evaluation by a recognized agency. The distinction here is critical; a listed device must have tangible proof of its reliability and effectiveness as established through rigorous testing procedures.

Therefore, a fire protection component used generally in residential areas does not provide the necessary context of having undergone testing or meeting specific standards set by an authoritative body. This is why it is categorized as not a listed device, highlighting the importance of compliance with recognized testing standards in ensuring fire safety.