Arduino Co2 detector MH-Z19b connected to Blynk via ESP8266

arduino-d1-mini-mhz19b.ino

#define BLYNK_PRINT Serial                     
#include <SoftwareSerial.h>  
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>
#include <MHZ19PWM.h>

MHZ19PWM mhz(D5, MHZ_DELAYED_MODE);

char auth[] = "dM-aERE2i1ZZd-aauogHCQXcGloNdNSi";
char ssid[] = "Mosne_2G";
char pass[] = "18031982";

BlynkTimer timerData;

void timerDataEvent()
{
    float ppm = mhz.getCO2();
    Serial.print(F("CO2: "));
    Serial.println(ppm);
    Blynk.virtualWrite(V5, ppm );
    
    if (ppm <= 400 || ppm > 4900) {
      Serial.println("Error: no data yet");          
    } else {
      if (ppm < 450) {   
        Serial.println("Very good");
      }
      else if (ppm < 600) {   
        Serial.println("Good");
      }
      else if (ppm < 1000) {   
        Serial.println("Acceptable");
      }
      else if (ppm < 2500) {   
        Serial.println("Bad, notification sent");
        Blynk.notify(String("Open the window! ") + String(ppm) + String("ppm!") );
        Serial.println(String("Open the window! ") + String(ppm) + String("ppm!"));
      }
     else {   
        Serial.println("Health risk");
      }
    }
 }


void setup()
{
  // Debug console
  Serial.begin(115200);
  Serial.println(F("Starting..."));
  Blynk.begin(auth, ssid, pass);
  delay(2000);
  mhz.useLimit(2830); // 5000>708
  timerData.setInterval(10000L, timerDataEvent);
}

void loop()
{
  Blynk.run();
  timerData.run(); 
}