This is a simple to use Carbon Monoxide (MQ-7). The sensor has a simple analog output and needs no additional complex circuitry to get it working. Just power the sensor with 5V, as explained in the product datasheet, add a load resistor, and you will get an analog output corresponding to the concentration of the gas.
Note: The sensor comes in an odd 6 pin package and it may be tough to solder it onto a PCB. You may have to directly solder wires to the sensor or alternatively use our LPG Sensor Module.