This is a simple circuit to build a smoke detector. It mainly uses MQ6 Smoke/Gas sensor to detect the level of smoke. MQ6 gas sensor is also sensible to LPG, Alcohol, and Methane etc. Here we have used Buzzer as a Smoke alarm, which is driven by BC547 NPN transistor. For complete details about this circuit and build yourself, check this link: [Simple smoke detector circuit][1] [1]: https://circuitdigest.com/electronic-circuits/simple-smoke-detector-alarm-circuit-diagram