In what location must rigid, metal, nonmetallic or intermediate conduit be used?

Rigid, metal, nonmetallic, or intermediate conduit must be used in hoistways to ensure safety and compliance with electrical codes. Hoistways are often subject to mechanical stresses from moving machinery, such as elevators. Using robust types of conduit like rigid or intermediate conduit provides better protection against physical damage, environmental factors, and helps contain any potential fire hazards.

In contrast, while electrical rooms, HVAC units, and rooftops may have specific requirements regarding conduit use, they are not as stringent as those required for hoistways. In electrical rooms, for instance, there's typically a greater emphasis on wiring methods appropriate for lower-risk environments, and HVAC units might allow for more flexible conduit systems. On rooftops, various materials could be utilized depending on the installation specifics and building codes but are generally less demanding for robust conduit types compared to hoistways. Thus, the use of more durable conduit types in hoistways is a critical safety measure in fire alarm system installations.