Attributes

Brand	-
Category	Robotics / STEM Teaching Tools / Sensors
Origin	-
Model Number	MQ-135
Detection Gases	Ammonia, NOx, Alcohol, Benzene, Smoke, CO2
Operating Voltage	5V DC
Interface Type	Analog and Digital Output
Preheat Time	24-48 Hours
Load Resistance	20k Ohm (Adjustable)
Heater Resistance	33 Ohm +/- 5%
Heater Consumption	< 800mW
Sensing Range	10-1000 ppm
Board Dimensions	32mm x 20mm x 14mm

6 reviews

Anonymous

Mar 31, 2026

Rating: 4/5

Good value but needs calibration

Great little module for the price. The digital output threshold is adjustable via the potentiometer which is handy. It took some trial and error to get the baseline right for my specific room, but once set, it's reliable.

Anonymous

Mar 29, 2026

Rating: 5/5

Excellent for university projects

Bought this for my final year project on smart home safety. It detects smoke and alcohol vapors effectively. The documentation online is plentiful, making integration easy even for beginners.

Anonymous

Mar 28, 2026

Rating: 5/5

Perfect for Air Quality Projects

This sensor works exactly as described. I used it with an Arduino to monitor indoor air quality, and the analog readings are very responsive to changes in the environment. Just remember to let it preheat for a day before calibrating.

Anonymous

Mar 25, 2026

Rating: 3/5

Sensitive but drifts over time

It is very sensitive to ammonia and fertilizers which is what I needed. However, I noticed the baseline drifts after a few weeks, requiring recalibration. Good for prototyping, maybe not for long-term unattended deployment without maintenance.

Anonymous

Mar 05, 2026

Rating: 4/5

Solid sensor module

Does the job for detecting combustible gases and general air pollutants. The heater gets quite warm, which is normal for this type of sensor. Ensure your power supply can handle the current draw.

Anonymous

Mar 01, 2026

Rating: 5/5

Fast shipping and works great

Arrived well-packaged. Connected it to my Raspberry Pi via an ADC converter. It picks up on cooking fumes immediately. The build quality of the PCB looks solid with clear soldering points.

5 FAQ

Q: Does this come with a library for Arduino?

A: We do not provide a proprietary library, but there are many open-source libraries available in the Arduino Library Manager compatible with MQ sensors. They make reading the analog values and converting them to ppm estimates very easy.

Q: How long does the preheating process actually take?

A: For stable and accurate readings, we recommend a preheating period of 24 to 48 hours. During this time, the sensor element stabilizes. You might see fluctuating values if you try to use it immediately out of the box.

Q: Can I power this with 3.3V instead of 5V?

A: No, the heater element requires 5V to reach the correct operating temperature for the chemical reaction to occur. Powering it with 3.3V will result in poor sensitivity or no detection at all. Use a 5V supply.

Q: Is the digital output pin HIGH or LOW when gas is detected?

A: By default, the digital output goes LOW when the gas concentration exceeds the threshold set by the potentiometer. However, this logic can often be inverted depending on how you interface it with your microcontroller code.

Q: Can this sensor detect natural gas leaks specifically?

A: The MQ-135 is primarily designed for ammonia, NOx, alcohol, benzene, smoke, and CO2. While it may react to some combustible gases, for dedicated natural gas (methane) detection, the MQ-5 or MQ-6 models are more appropriate and accurate.

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