TC reported external smoke pre alarm atthe car front M1. Staff(YCK) checked and confirmed there wer e no heat and no smoke. No abnormalities. ~~~~~ Check Tims observed FC-777- External smoke pre-alarm 2 activated. Further check found sensor was dirty. Conduct cleaning ok. Function test ok. To be further monitoring on M/L. Done by Deeshan/Sanip/Faddzal. 06/05/21.