diff --git a/MH-Z19B.ino b/MH-Z19B.ino
index d47b5ad..63d2c97 100644
--- a/MH-Z19B.ino
+++ b/MH-Z19B.ino
@@ -26,16 +26,23 @@ void loop() {
   // Serial.print("\n----- Time from start: ");
   // Serial.print(millis() / 1000);
   // Serial.println(" s");
+
   int ppm_uart = co2.readCO2UART();
+  if (ppm_uart > 0) {
+    Serial.print("PPMuart: ");
+    Serial.print(ppm_uart);
+  }
+
   // int ppm_pwm = co2.readCO2PWM();
-  int temperature = co2.getLastTemperature();
-  Serial.print("PPMuart: ");
-  Serial.print(ppm_uart);
   // Serial.print(", PPMpwm: ");
   // Serial.print(ppm_pwm);
-  Serial.print(", Temperature: ");
-  Serial.println(temperature);
+
+  int temperature = co2.getLastTemperature();
+  if (temperature > 0) {
+    Serial.print(", Temperature: ");
+    Serial.println(temperature);
+  }
 
   // Serial.println("\n------------------------------");
-  // delay(3000);
+  delay(1000);
 }
diff --git a/MHZ.cpp b/MHZ.cpp
index 2dcb8ec..05c7119 100644
--- a/MHZ.cpp
+++ b/MHZ.cpp
@@ -84,28 +84,30 @@ int MHZ::readCO2UART() {
     Serial.println(response[8], HEX);
     Serial.print("MHZ: Should be: ");
     Serial.println(check, HEX);
+    temperature = -1; // TODO maybe change to another magic value
+    return -1;
   }
 
   int ppm_uart = 256 * (int)response[2] + response[3];
 
   temperature = response[4] - 44; // - 40;
 
+  byte status = response[5];
   if (debug) {
     Serial.print(" # PPM UART: ");
     Serial.println(ppm_uart);
     Serial.print(" # Temperature? ");
     Serial.println(temperature);
+  }
 
-    // status
-    // not sure about this...
-    byte status = response[5];
-    Serial.print("  Status? ");
-    Serial.print(status);
-    if (status == 0x40) {
-      Serial.println(" - Status OK");
-    } else {
-      Serial.println(" ! Status not OK !");
-    }
+  // Is always 0 for version b
+  // Version a: status != 0x40
+  if (debug || status != 0) {
+    Serial.print(" ! Status not OK ! ");
+    Serial.println(status, HEX);
+  } else if (debug) {
+    Serial.print(" Status  OK: ");
+    Serial.println(status, HEX);
   }
 
   return ppm_uart;