Section 25.1731 - Powerplant and APU fire detector system: EWIS(a) EWIS that are part of each fire or overheat detector system in a fire zone must be fire-resistant.(b) No EWIS component of any fire or overheat detector system for any fire zone may pass through another fire zone, unless:(1) It is protected against the possibility of false warnings resulting from fires in zones through which it passes; or(2) Each zone involved is simultaneously protected by the same detector and extinguishing system.(c) EWIS that are part of each fire or overheat detector system in a fire zone must meet the requirements of § 25.1203 .