MQ-3 Alcohol Sensor

The MQ-3 Alcohol Sensor is a low-cost semiconductor gas sensor designed for detecting alcohol vapour in air. It is suitable for hobby electronics, Arduino projects, ESP32 projects, educational experiments, alcohol detector prototypes, and general gas-sensing demonstrations.

The sensor element uses tin dioxide (SnO2) as the gas-sensitive material. In clean air, the material has relatively low conductivity. When alcohol vapour is present, the conductivity of the sensor increases as the alcohol concentration rises. With a simple external circuit, this change can be converted into an analog voltage signal that can be read by a microcontroller or comparator circuit.

The MQ-3 Alcohol Sensor is especially sensitive to alcohol gas and is designed to reduce interference from gasoline, smoke, and water vapour compared with more general-purpose gas sensors. It is best suited for alcohol vapour detection projects, not for identifying or measuring every possible gas in the environment.

Download MQ-3 Sensor Datasheet (PDF)

Typical applications:

• Arduino, ESP32, Raspberry Pi, and other microcontroller alcohol-sensing projects
• Alcohol detector prototypes
• Breath alcohol experiment projects
• Educational gas sensor demonstrations
• Portable alcohol detector projects
• Domestic or industrial alcohol vapour alarm prototypes
• Analog sensor experiments and comparator-based alarm circuits

Helpful information:

• The MQ-3 is not a digital sensor. The sensing element changes resistance depending on alcohol vapour concentration.
• A load resistor is required to convert the sensor resistance change into a measurable voltage.
• The heater draws noticeable current. Make sure your 5V supply can provide enough power.
• The sensor needs warm-up time. Readings directly after power-up may drift and should not be treated as stable measurements.
• For more repeatable measurements, allow the sensor to stabilize before taking readings.
• Temperature, humidity, airflow, sensor age, and previous exposure to gases can affect readings.
• The MQ-3 is suitable for detecting alcohol vapour, but it is not a laboratory-grade alcohol analyser.
• For accurate concentration readings, calibration against a known reference gas or known test setup is required.

Basic operating principle:

• The heater brings the sensing material to its required operating temperature.
• The sensing resistance changes when alcohol vapour is present.
• The external load resistor converts this resistance change into a voltage.
• The voltage can be connected to an analog input of a microcontroller or to a comparator circuit.

Recommended handling and operating precautions:

• Avoid exposure to silicone vapours, silicone adhesives, silicone rubber, putty, or plastics containing silicone. Silicone contamination can permanently reduce sensor sensitivity.
• Avoid highly corrosive gases such as H2S, SOx, Cl2, and HCl.
• Avoid contamination from alkali materials, alkali metal salts, salt spray, halogens, or similar harsh chemicals.
• Do not expose the sensor to water, condensation, freezing conditions, or direct liquid contact.
• Do not apply voltages above the rated values.
• Avoid long-term storage in polluted, humid, or high-temperature environments.
• Avoid strong vibration, shock, or dropping the sensor.
• Do not test the sensor by directly spraying lighter gas or highly concentrated vapours onto it. Very high gas concentrations can damage or degrade the sensor.

Important safety note:

This sensor is intended for electronics projects, prototyping, education, and experimental alcohol vapour detection. It is not a ready-made certified breathalyser, safety alarm, workplace safety device, or law-enforcement measuring instrument. For legal, medical, workplace, or life-safety applications, use properly certified equipment.