TIMS showed Smoke External Alarm at car1546. Staff(KTB) checked and confirmed no signs of smoke on exterior or interior of train. Rear T237 line clear and conf irmed no abnormalities. ~~~~~ 1546 TIMS showed Smoke External Alarm. Staff(KTB) confirmed no signs of smoke on exterior/interior of train. Rear T237 line clear and confirmed no abnormalities. CE : Reset monitored ok.  1546 TIMS showed FC 721 (Smoke External) Alarm. Opened filter cover at hatch cover to check on external smoke detector & found no sign of water ingress or any rust. Found smoke detector cover seal (terminal side) missing. Swappped fire relay panel from #1546 to #3546. OPS 20 raised to replace smoke detector seal.  Sugu/Sarma/Anand 45073 Fire Relay Panel S/N : (after swapped) #3546 - 155 #1546 - 154 To install cable gland and plaseal     #1546 Replaced smoke detector exterior and function test and plaseal ok. Not: 2493413 raise. Done by Kamal/Nabil/Firas/Imran.  31/05/23