The MQ-2 Smoke Gas Sensor is a low-cost, highly sensitive semiconductor gas detection module designed for monitoring flammable gases and smoke in domestic, industrial, and automotive environments. Built around the MQ-2 sensor with a tin dioxide (SnO₂) sensing layer, this module responds to a broad range of combustible gases including LPG, propane, butane, methane, hydrogen, alcohol vapors, and smoke. It is an ideal solution for home gas leak alarms, kitchen safety systems, fire detection prototypes, and educational sensor projects.
At the heart of the module is the MQ-2 sensor element, whose conductivity increases as the concentration of target gases rises. In clean air, the sensor exhibits low conductivity; when exposed to flammable gases or smoke, its resistance drops, producing a measurable change in output. The module provides two independent outputs: an analog output (AO) that varies continuously with gas concentration for trend monitoring, and a digital output (DO) that switches when the concentration exceeds a user-adjustable threshold set by the onboard potentiometer. This dual-output design makes it suitable for both quantitative trend analysis and simple threshold-based alarm triggering.
The module operates from 5V DC with a typical current consumption of approximately 150mA. It is compatible with Arduino, ESP32, and other 5V microcontrollers; Raspberry Pi users require an external ADC. The board features a compact form factor and an onboard LED indicator that provides visual feedback for power and digital output status.
Important Note: The MQ-2 requires a significant preheat time for stable operation. New sensors should be powered on for 24–48 hours in clean air before initial calibration. After each power-up, allow at least 20 seconds to 5 minutes for the heater to stabilize. The sensor is not selective — it cannot distinguish between specific gases and responds to all reducing gases. It is not a calibrated industrial-grade detector and should not be used as a sole life-safety device. Its sensitivity degrades over time, and periodic replacement is recommended for critical applications. The sensor surface becomes hot during operation — avoid touching it. The module is not waterproof and should be kept dry.
Whether you are building a home gas leak alarm, a kitchen safety system, or an educational sensor project, the MQ-2 module provides a reliable, affordable solution for broad-spectrum flammable gas and smoke detection.
Features
-
MQ-2 SnO₂ semiconductor sensor — High sensitivity to LPG, propane, butane, methane, hydrogen, alcohol, and smoke
-
Dual output — Analog (AO) for concentration trends, Digital (DO) for threshold alarms
-
Adjustable threshold — Onboard potentiometer sets the digital output trigger point
-
Wide detection range — 300–10,000 ppm for flammable gases
-
5V operation — Compatible with Arduino, ESP32, and other 5V microcontrollers
-
LED indicators — Power and digital output status feedback
-
Compact form factor — 32 × 20mm PCB for easy integration
-
Fast response — Quick detection of gas concentration changes
-
Long lifespan — Specified for up to 10 years under proper operating conditions
-
Wide application range — Home gas alarms, kitchen safety, industrial monitoring, education
Technical Specifications
Usage
Getting Started
-
Connect power — Connect VCC to 5V and GND to ground. The onboard power LED should light up.
-
Connect outputs — Connect AO to an analog input on your microcontroller (e.g., A0 on Arduino) and DO to a digital input if threshold detection is needed.
-
Preheat — Allow the sensor to warm up. For first-time use, power it in clean air for 24–48 hours for best accuracy. For normal use, wait at least 5–10 minutes before taking readings.
-
Calibrate (recommended) — In clean outdoor air, note the analog reading. Adjust the onboard potentiometer so the DO output switches just above this baseline.
-
Read data — Use analogRead() for concentration trends, or digitalRead() for threshold-based alarms.
-
Implement control logic — Trigger buzzers, fans, or notifications when the sensor value exceeds your defined threshold.
Pin Connections
Example Arduino Code (Basic Reading)
#define MQ2_AO A0
#define MQ2_DO 8
void setup() {
Serial.begin(9600);
pinMode(MQ2_DO, INPUT);
}
void loop() {
int analogValue = analogRead(MQ2_AO);
int digitalState = digitalRead(MQ2_DO);
Serial.print("Gas Level: ");
Serial.print(analogValue);
Serial.print(" | Alarm: ");
Serial.println(digitalState == LOW ? "TRIGGERED" : "Normal");
delay(1000);
}
Typical Applications
-
Home LPG leak detection — Place near gas appliances or cylinders; trigger alarm when concentration exceeds safe levels
-
Kitchen safety system — Detect smoke from burnt food before it triggers a smoke detector; activate exhaust fans
-
Industrial gas monitoring — Monitor propane, methane, or hydrogen in workshop environments
-
Vehicle exhaust detection — Monitor CO levels in enclosed garages and tunnels
-
Educational STEM projects — Teaching analog sensing, gas detection, and calibration principles
Notes for Business Buyers
-
Preheat is essential — The 24–48 hour initial burn-in is critical for stable readings; factor this into production testing timelines
-
Not a precision instrument — MQ sensors provide relative trend data, not exact ppm readings for specific gases
-
Sensor lifespan — Sensitivity degrades over time (typically 2–3 years depending on exposure); plan for periodic replacement
-
Suitable for bulk purchasing — Ideal for gas alarm manufacturers, educational kit suppliers, and smart home product developers
Q: What is the MQ-2 sensor used for?
It is a gas sensor for detecting flammable gases (LPG, propane, butane, methane, hydrogen, alcohol) and smoke in home gas alarms, kitchen safety systems, and industrial monitoring.
Q: What is the difference between the analog and digital outputs?
AO provides a continuous voltage that increases with gas concentration for trend monitoring. DO switches LOW when the concentration exceeds the onboard potentiometer threshold, ideal for simple alarms.
Q: Why does the sensor need a long preheat time?
The SnO₂ sensing element requires heating to reach stable operating temperature. First-time use needs 24–48 hours for accurate calibration; each power-up needs at least 5–10 minutes to stabilize.
Q: Can I measure exact ppm with this sensor?
Not accurately without calibration. The MQ-2 is non-selective and provides relative trends. For quantitative measurement, you need calibration curves and cross-sensitivity compensation.
Q: What voltage does the module require?
It operates from 5V DC with approximately 150mA current consumption
Q: How do I calibrate the digital output threshold?
Power the sensor in clean air, note the AO reading, then adjust the onboard potentiometer until the DO output switches at a slightly higher level.
Q: Is the sensor safe to touch?
No. The sensor surface becomes hot during operation due to the internal heater. Avoid touching it.
Q: Can I use this module with a Raspberry Pi?
Yes, but the Pi lacks a built-in ADC. Use an external ADC (e.g., MCP3008) to read the AO output.
Q: How long does the sensor last?
The sensor is specified for up to 10 years under proper conditions, but practical lifespan is often 2–3 years depending on exposure to contaminants.
Q: Can I purchase in bulk for a product development project?
Yes. This module is suitable for bulk purchasing by gas alarm manufacturers, educational kit suppliers, and smart home product developers.
