This fire alarm system project is used to detect a fire and generate an alarm to alert the people in the buildings, offices and where it is installed. This project uses a BC177 transistor to sense the heat produced due to the fire. A preset level can be kept for the BC177 transistor. When the temperature increases above the set preset level, the leakage current of the transistor also increases, to make the other transistors in the circuit. A relay is used to switch the bell load as its o/p.