The MQ-6 is a MOS gas sensor optimized for LPG, propane, and isobutane (200–10,000 ppm). It uses a SnO₂ sensing element heated by a Ni-Cr coil—resistance drops when target gases are present. The breakout board provides a 0–5V analog output (AO) and a potentiometer-adjustable digital output (DO) via an LM393 comparator.