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Home / Sensors / MQ-135 Air Quality Sensor MQ135 Sensor Harmful Gas Detection Module

Attributes

Brand -
Category Robotics / STEM Teaching Tools / Sensors
Origin -
Model Number MQ-135
Detection Gases Ammonia, Sulfide, Benzene, Smoke, CO2
Operating Voltage 5V DC
Output Signal Analog and Digital (TTL)
Heater Voltage 5.0V ± 0.2V
Load Resistance Adjustable via Potentiometer
Preheat Time Over 24 hours for stability
Interface Type 3-Pin Header (VCC, GND, OUT)
PCB Dimensions 32mm x 20mm
Application Air Quality Monitoring Systems

6 reviews

A

Anonymous

Mar 31, 2026

Rating: 4/5

Good value but needs calibration

The module is well-built and the potentiometer makes it easy to adjust sensitivity. Just remember it takes a day or two to stabilize readings accurately.

A

Anonymous

Mar 27, 2026

Rating: 5/5

Perfect for ventilation control

Integrated this into my greenhouse ventilation system to monitor ammonia levels. It has been running continuously for weeks without issues.

A

Anonymous

Mar 26, 2026

Rating: 3/5

Works but gets hot

The sensor functions correctly, but the heating element gets quite warm, which is normal for this type but worth noting for enclosed cases.

A

Anonymous

Mar 24, 2026

Rating: 5/5

Reliable gas detection

I used this to detect smoke and cooking fumes in my kitchen prototype. It reacts quickly to changes in air quality. Highly recommended for hobbyists.

A

Anonymous

Mar 17, 2026

Rating: 5/5

Great for Arduino projects

This sensor works perfectly with my Arduino Uno. The analog output is stable after the initial preheat time. Easy to integrate into home air quality monitors.

A

Anonymous

Mar 16, 2026

Rating: 4/5

Solid performance

Works as described. The digital output threshold is adjustable which is a nice feature. Make sure you have a proper 5V power supply.

5 FAQ

Q: How long does the preheat time really need to be?

A: For accurate and stable readings, we recommend a preheat time of at least 24 to 48 hours. Initial readings may fluctuate significantly before this period.

Q: Can this detect Carbon Monoxide (CO)?

A: The MQ-135 is primarily sensitive to Ammonia, Sulfide, and Benzene. While it has some sensitivity to CO, the MQ-7 sensor is specifically designed for Carbon Monoxide detection.

Q: Is the library available for Raspberry Pi?

A: Yes, since it outputs an analog signal, you will need an ADC (Analog-to-Digital Converter) chip like the MCP3008 to interface with the Raspberry Pi GPIO pins.

Q: What is the lifespan of the heating element?

A: Under normal operating conditions, the heating element typically lasts for several years. Continuous operation within the specified voltage range ensures maximum longevity.

Q: Does this module work with 3.3V microcontrollers like ESP32?

A: Yes, but you may need a voltage divider or level shifter for the output signal since the sensor operates at 5V. The heater specifically requires 5V.

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