# Air quality sensor MQ-135

> MQ-135 air quality sensor module, based on SnO2, whose conductivity changes according to pollution level. Detects ammonia, gasoline vapors, smoke and other harmful gases. Power supply 5VDC, current draw about 50mA. Provides an analog output 0-5V for continuous measurement and a digital TTL output for settable thresholds. Easy to integrate with Arduino and other microcontrollers.

- Page: https://sigmanortec.ro/en/air-quality-sensor-mq-135
- Price: 14.94 RON
- Availability: In stock; 1-2 zile
- Reference: 22139 · EAN: 5944647993200
- Category: Mechatronics and IoT > Sensors and Modules > Gas and Air Quality Sensors
- Package (shipping data): 0.008 kg
- Updated: 2026-09-14
- Shop: [Sigmanortec.ro](https://sigmanortec.ro/en/llms.txt)
- Prices: RON, VAT included; prices and stock as of 2026-10-22 01:33 (Europe/Bucharest)

## Description

Air quality monitoring module, detects ammonia, gasoline vapor, smoke and other harmful gases, based on SnO2 which changes its conductivity depending on the pollution level. It operates at 5V with low consumption, offers 0-5V analog output for continuous measurement and TTL digital output for settable thresholds, easy to integrate with Arduino and other microcontrollers.
MQ135 sensor used for air quality detection.
Detects harmful particles in the air such as: ammonia, gasoline vapors, smoke and other harmful gases.
It uses the Tin Dioxide (SnO2) incorporated in the sensor, which has a low conductivity in clean air; the more polluted the air, the higher the conductivity.
Specifications:
Supply voltage: 5VDC, a50mA
Output: Digital pin or Analog pin
Analog output: 0 - 5V; the voltage increases or decreases depending on the detected concentration
TTL Digital Output
Analogue reading code example:
void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
}
// the loop routine runs over and over again forever:
void loop() {
// read the input on analog pin 0:
int sensorValue = analogRead(A0);
// print out the value you read:
Serial.println(sensorValue);
delay(1); // delay in between readings for stability
}