Introduction

Ensuring the safety and health of employees working in a garage is crucial due to potential exposure to harmful gases and pollutants. Monitoring air quality can help maintain a safe working environment. In this guide, we will use the MQ135 air quality gas sensor with an Arduino to monitor air quality in a garage and protect the employees inside.

What is an Air Quality Sensor?

An air quality sensor is a device used to measure and detect various pollutants present in the air. These pollutants can include gases such as carbon monoxide (CO), nitrogen dioxide (NO2), and volatile organic compounds (VOCs), as well as particles like dust and pollen. Air quality sensors typically work by measuring changes in resistance, conductivity, or voltage caused by the presence of pollutants in the air. The output of the sensor is then processed and converted into numerical readings that can be used to evaluate air quality.

What is an MQ135 Air Quality Gas Sensor?

The MQ135 Semiconductor Sensor is highly sensitive to ammonia gas, sulfide, benzene series steam, smoke, and other toxic gases. It uses SnO2 semiconductor material to detect these gases, which has lower conductivity in clean air and increases in conductivity as gas levels rise. This change can be converted into gas concentration through a simple electronic circuit.

Applications

• Air quality control in garages
• Domestic gas alarms
• Industrial gas alarms
• Portable gas detectors

Working of the System with Arduino

The MQ135 air quality gas sensor operates by detecting changes in the conductivity of its SnO2 semiconductor material when exposed to various gases. In clean air, the conductivity is low, but it increases as the concentration of gases rises. This change in conductivity can be measured and converted into a gas concentration reading, allowing for real-time monitoring of air quality.

Specifications – MQ135

Feature	Description
Operating Voltage	2.5-5.0V
Detecting Concentration	10ppm-300ppm for NH3 10ppm-1000ppm for Benzene 10ppm-300ppm for Alcohol
Load Resistance	Adjustable
Heater Resistance	33Ω ± 5%
Heater Consumption	less than 800mW
Operating Temperature	-10 to 45°C

Things We Need

1. Arduino Uno or compatible microcontroller.
2. MQ135 Air Quality Sensor.
3. Breadboard
4. Jumper Wires
5. USB cable
6. 16×2 I2C LCD Display
7. I2C Module for the LCD

Circuit Diagram

To monitor the air quality in the garage, connect the MQ135 sensor and the I2C LCD to an Arduino as follows:

Code

Here’s a simplified example of Arduino code for this system:

Please include LiquidCrystalI2C Library before uploading the code and make sure that you change the address of the LCD in the Code. (Example : The below code has 0x27 as the address)

If you are new to LCD please refer to How to Connect an LCD with the Arduino

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

int sensorPin = A0;
int sensorData;

void setup() {  
  lcd.begin();
  lcd.backlight();
  Serial.begin(9600);   
  pinMode(sensorPin, INPUT);                         
}

void loop() {
  sensorData = analogRead(sensorPin);       
  lcd.setCursor(0, 0);
  lcd.print("Air Quality:");
  lcd.setCursor(0, 1);
  lcd.print(sensorData);
  lcd.print(" PPM");
  delay(1000);                                   
}

Conclusion

By integrating the MQ135 air quality sensor with an Arduino and displaying the data on an I2C LCD, you can effectively monitor the air quality in a garage to ensure it meets safety standards. This setup will help protect employees from harmful gases and pollutants, contributing to a safer working environment. Regular monitoring and timely alerts can prevent hazardous conditions, thereby safeguarding the health of those in the garage.