MQ135 Air Quality Gas Sensor Module

MQ135 Air Quality Gas Sensor Module ($\text{NH}_3$, $\text{CO}_2$, Smoke Detection)

The MQ135 Air Quality Gas Sensor Module is a versatile semiconductor sensor designed for wide-ranging detection of air pollutants and hazardous gases. It is highly sensitive to compounds like Ammonia ($\text{NH}_3$), Nitrogen Oxides ($\text{NO}_\text{x}$), Alcohol, Benzene, and smoke, making it an essential component for monitoring the overall air quality in homes, offices, and industrial settings.

 

The sensor operates by measuring the change in conductivity of its $\text{SnO}_2$ sensing element when exposed to target gases. The module includes a built-in heater and circuitry, along with an LM393 comparator chip, to provide both an analog reading (for parts-per-million, or PPM estimation) and a direct digital switch signal.

 

🔧 Key Features

• Target Gases:Ammonia, Sulfide, Benzene, Alcohol, Smoke, and $\text{CO}_2$ (toxic gases).
   
• Sensing Element: $\text{SnO}_2$ (Tin Dioxide) semiconductor material.
   
• Dual Output: Provides Analog Output (AO) for concentration and Digital Output (DO) for threshold detection.
   
• Operating Voltage: Standard $5 \text{V}$ DC (typical).
   
• Sensitivity: Adjustable via onboard potentiometer to set the digital switch threshold.
   
• Signal: The digital output is a TTL-level signal, typically LOW when gas concentration exceeds the threshold.
   
• Stability: Features fast response and recovery characteristics with long service life.
  

💡 Applications  

• Indoor Air Quality Monitoring and pollution detection devices.
   
• Building Ventilation Control Systems that react to pollutant levels.
   
• Smoke and Fire Detection systems (sensitive to general smoke/fumes).
   
• Educational and DIY projects involving Environmental Sensing with Arduino/Raspberry Pi.
 

 

⚙️ Technical Specifications

                                                                   

Sensor Model	MQ135
Operating Voltage	$2.5 \text{V}$ to $5.0 \text{V}$ DC ($5 \text{V}$ typical)
Target Gas Concentration	$10 \text{ ppm} \sim 1000 \text{ ppm}$ ($\text{NH}_3$, Benzene, Alcohol)
Output Type	Analog (0V-5V) and Digital (TTL)
Preheat Time	$20$ seconds to $24$ hours (Required for stability/accuracy)
Operating Current (Typical)	$\approx 150 \text{ mA}$ (Heating consumption)
Comparator Chip	LM393
Interface Pins	VCC, GND, AO, DO (4-Pin Header)

 

📦 Package Includes

• 1 × MQ135 Air Quality Gas Sensor Module