This part is a kind of semiconductor called MQ-303A.

Function of this product has GAS SENSOR.

Manufacturers : HANWEI ELETRONICS

Image and pinout :

Some of the text within the PDF file :

HANWEI ELETRONICS CO.,LTD MQ-303A http://www.hwsensor.com GAS SENSOR MQ-303A for ALCOHOL DETECTION * High sensitivity * Low power consumption * Miniature-size The MQ-303A is a tin dioxide semiconductor gas sensor which has a high sensitivity to alcohol with quick response speed. This model is suitable for alcohol detection such as portable breath alcohol checker or ignition locking system in automobiles. Structure Gas sensitive semiconductor material is a mini bead type and a heater coil and electrode wire are embedded in the element. The sensing element is installed in the metal housing which uses double stainless steel mesh (100 mesh) in the path of gas flow. The mesh is an anti-explosion feature (Fig 1). Operating conditions Fig 2 shows the standard operating circuit for this model [ ... ]

MQ-303A PDF Datasheet Download