What is defined as an assembly of piping, conduits, or containers that suppresses or extinguishes fires?

The definition provided describes a fixed fire extinguisher system accurately. This type of system is designed to automatically suppress or extinguish fires in designated areas using a network of fixed piping or conduits connected to a fire suppression agent, such as water, foam, or chemicals. It is installed in a permanent location and is engineered to activate under specific fire conditions, allowing for immediate response to a fire threat without relying on human intervention.

In contrast, a portable fire extinguisher typically refers to a movable, hand-held device that an individual can use to combat smaller fires. While important for fire safety, it does not involve the complex assembly of piping or conduits characteristic of fixed systems. Fire suppression devices could refer to a range of equipment used to combat fire but do not encompass the idea of a comprehensive system as indicated in the question. A hydrostatic testing unit is primarily related to the testing of pressurized systems for leaks and is not designed for fire suppression. Hence, the emphasis on an assembly for effective fire suppression points clearly to a fixed fire extinguisher system as the correct response.