First Alert HD6135FB BRK Brands Hardwired Heat Alarm with Battery Backup | First Alert Store
Heat Alarm (Interconnectable) - 9v Battery Back Up Hispec | Meteor Electical
Heat Detectors
Ei Heat Detector – Dwyers
AJ Interlinked Heat Alarm & Smoke Alarm Extended Bundle, 10-Year Tamper-Proof Battery - SAFE-TECH - A British Brand Specialising in Home and Safety Protection
5809SS Fixed Heat and Rate-of-Rise Detector, Honeywell - - Amazon.com