TC reported fire external at Rear M1 car. Staff(BSH) checked negative. No sign of fire and no abnorm alities. Rear T204 line clear feedback no abnormalities. ~~~~~ TC reported fire external at Rear M1 car SDR11 removed, isolated and ADDL shortloop Ops20 to check fire smoke detector for water/dust ingress To check ext smoke detector for water/dust ingress Checked 1565 external smoke detector found dusty. Preventively replaced FSD to further monitor in mainline. Notification to CSC: 2505228 Saini/Asruddin 12.7.23