Available sensor e.g. https://www.dfrobot.com/product-2512.html This one supports UART and i2c as well as setting a value and getting an alarm signal. Addt. info on the wiki: https://wiki.dfrobot.com/SKU_SEN0465toSEN0476_Gravity_Gas_Sensor_Calibrated_I2C_UART
Available sensor e.g. https://www.dfrobot.com/product-2512.html
This one supports UART and i2c as well as setting a value and getting an alarm signal.
Addt. info on the wiki: https://wiki.dfrobot.com/SKU_SEN0465toSEN0476_Gravity_Gas_Sensor_Calibrated_I2C_UART