   float t = dht.readTemperature();
 
   {
-    Serial.print(millis()/1000);
+    Serial.print(millis()/1000);  // elapsed seconds since boot
     Serial.print(",");
     Serial.print(h,1);
     Serial.print(",");

    Serial.print(",");
    Serial.print(vol_Formol,3);
    Serial.println("");
  }
  {
    SeeedOled.clearDisplay();

float concentration = 0;
int sensorValue = 0;

#define DHTPIN A2  //defining temp and humi sensor analog pin
#define DHTTYPE DHT11  //define the type of sensor. check the specsheet and seeed wiki
DHT dht(DHTPIN, DHTTYPE);

void setup() {
