MQ135 Air Quality Gas Sensor Module
- Highly sensitive to a wide range of harmful gases including NH₃, NOₓ, alcohol, benzene, smoke, and CO₂
- Provides dual output: analog signal for gas concentration and digital output for threshold-based detection
- Built around the LM393 comparator with an onboard potentiometer for adjustable sensitivity
- Operates on a standard 5V DC supply, compatible with most microcontrollers
- Ideal for indoor air quality monitoring, pollution detection, and environmental sensing projects
- Easy 4-pin interface (VCC, GND, AO, DO) for quick integration
Product Details
MQ135 Air Quality Gas Sensor Module (NH₃, CO₂, Smoke Detection)
The MQ135 Air Quality Gas Sensor Module is a versatile semiconductor-based sensor designed for detecting a wide range of air pollutants and harmful gases. It is highly sensitive to gases such as ammonia (NH₃), nitrogen oxides (NOₓ), alcohol vapors, benzene, smoke, and carbon dioxide (CO₂), making it an effective solution for monitoring indoor air quality in residential, commercial, and industrial environments.
The sensor operates using a tin dioxide (SnO₂) sensing element whose electrical conductivity changes in the presence of target gases. The onboard heater ensures stable operation, while the integrated LM393 comparator enables both continuous analog measurement and threshold-based digital detection. This dual-output design allows the module to function either as a quantitative air-quality sensor or a simple gas-triggered switch.
🔧 Key Features
- Multi-Gas Detection: Sensitive to NH₃, NOₓ, alcohol, benzene, smoke, and CO₂
- Semiconductor Sensing Element: SnO₂-based gas detection technology
- Dual Output:Analog Output (AO) for gas concentration estimation and Digital Output (DO) for threshold-based triggering
- Adjustable Sensitivity: Onboard potentiometer for setting digital trigger level
- Operating Voltage: Standard 5V DC, compatible with most microcontrollers
- Digital Logic: TTL-level output, typically LOW when gas concentration exceeds the set threshold
- Stable Performance: Fast response and recovery with long operational life
💡 Applications
- Indoor Air Quality Monitoring systems
- Environmental Pollution Detection devices
- Ventilation and Air Purification Control systems
- Smoke and Gas Leakage Detection
- Educational, research, and DIY environmental sensing projects
⚙️ Technical Specifications
| Sensor Model | MQ135 |
| Sensing Material | SnO₂ (Tin Dioxide) |
| Operating Voltage | 2.5V – 5.0V DC (5V typical) |
| Target Gas Range | 10 ppm – 1000 ppm (NH₃, benzene, alcohol, smoke) |
| Output Type | Analog (0–5V) and Digital (TTL) |
| Preheat Time | 20 seconds (minimum), up to 24 hours for optimal accuracy |
| Operating Current | ≈ 150 mA (heater consumption) |
| Comparator IC | LM393 |
| Interface Pins | VCC, GND, AO, DO |
📦 Package Includes
- 1 × MQ135 Air Quality Gas Sensor Module
Specifications
- TypeGas Sensor
- Operating Voltage3.3V – 5V
- Temperature Range−10∘C-45∘C
- Output TypeAnalog and Digital
- Sampling RateInstantaneous
- InterfaceVCC
