ZE08-CH2O

/*
The ZE08-CH2O is a formaldehyde gas sensor that detects the concentration of formaldehyde in the air. Here's an example code for Arduino that reads the formaldehyde concentration from the sensor:

Note: This code assumes that the ZE08-CH2O formaldehyde gas sensor is connected to pins 2 and 3 of the Arduino board for the software serial connection. If you're using different pins or a hardware serial connection, you'll need to modify the SoftwareSerial initialization and ch2oSerial object accordingly. Also, note that the sensor requires a warm-up time of at least 3 minutes after power-on before providing accurate readings, so be sure to wait for this period before reading from the sensor. Finally, note that the sensor is designed to detect formaldehyde specifically and may not detect other gases or vapors.

Please use a 5V to 3.3V logic level converter!
*/

#include <SoftwareSerial.h>

SoftwareSerial ch2oSerial(2, 3);  // RX, TX pins of the software serial connection to the sensor

void setup() {
  Serial.begin(9600);
  ch2oSerial.begin(9600);  // start the software serial connection to the sensor
}

void loop() {
  ch2oSerial.write("\xFF\x01\x78\x40\x00\x00\x00\x00\x47");  // request a formaldehyde concentration reading from the sensor
  delay(100);
  while (ch2oSerial.available() > 0) {
    if (ch2oSerial.read() == '\xFF') {
      if (ch2oSerial.read() == '\x17') {
        int ch2o_concentration = ch2oSerial.read() * 256;
        ch2o_concentration += ch2oSerial.read();
        Serial.print("Formaldehyde Concentration: ");
        Serial.print(ch2o_concentration);
        Serial.println(" ppb");
      }
    }
  }
  delay(1000);
}