Smoke & Gas Sensor for Electronics Projects- MQ2By Robolab Technologies In Arduino, Atal Tinkering Labs ATL
This project uses an Arduino NANO and a Nokia 5110 LCD screen for measuring and displaying levels. It would may a nice and simple smoke detector or alarm project.
I think this might be a good sensor for home automation projects and many other uses. You only need one pin to accept the output from the sensor so it will fit nicely into many electronics projects.