diff --git a/ampel-firmware/co2_sensor.cpp b/ampel-firmware/co2_sensor.cpp
index 31db6eec123de48a65b66780929dcae37c5d5841..cac1c780ca60e84685335b4a8fe70dfed09cb0f7 100644
--- a/ampel-firmware/co2_sensor.cpp
+++ b/ampel-firmware/co2_sensor.cpp
@@ -84,13 +84,13 @@ namespace sensor {
 
     Serial.print(F("Setting temperature offset to -"));
     Serial.print(abs(config::temperature_offset));
-    Serial.println(" K.");
+    Serial.println(F(" K."));
     scd30.setTemperatureOffset(abs(config::temperature_offset)); // setTemperatureOffset only accepts positive numbers, but shifts the temperature down.
     delay(100);
 
     Serial.print(F("Temperature offset is : -"));
     Serial.print(scd30.getTemperatureOffset());
-    Serial.println(" K");
+    Serial.println(F(" K"));
 
     Serial.print(F("Auto-calibration is "));
     Serial.println(config::auto_calibrate_sensor ? "ON." : "OFF.");
@@ -100,7 +100,7 @@ namespace sensor {
     Serial.println();
     Serial.print(F("Setting SCD30 timestep to "));
     Serial.print(config::measurement_timestep_bootup);
-    Serial.println(" s during acclimatization.");
+    Serial.println(F(" s during acclimatization."));
     scd30.setMeasurementInterval(config::measurement_timestep_bootup); // [s]
 
     sensor_console::defineIntCommand("co2", setCO2forDebugging, F(" 1500 (Sets co2 level, for debugging purposes)"));
@@ -120,7 +120,7 @@ namespace sensor {
     int32_t now = millis();
     Serial.print(F("Measurement time offset : "));
     Serial.print(now - previous_measurement_at - config::measurement_timestep * 1000);
-    Serial.println(" ms.");
+    Serial.println(F(" ms."));
     previous_measurement_at = now;
   }
 
@@ -189,7 +189,7 @@ namespace sensor {
     if (config::debug_sensor_states) {
       Serial.print(F("Changing sensor state: "));
       Serial.print(state_names[current_state]);
-      Serial.print(" -> ");
+      Serial.print(F(" -> "));
       Serial.println(state_names[new_state]);
     }
     current_state = new_state;
@@ -204,7 +204,7 @@ namespace sensor {
       Serial.println(F("Sensor acclimatization finished."));
       Serial.print(F("Setting SCD30 timestep to "));
       Serial.print(config::measurement_timestep);
-      Serial.println(" s.");
+      Serial.println(F(" s."));
       scd30.setMeasurementInterval(config::measurement_timestep); // [s]
     }
     if ((current_state == PREPARE_CALIBRATION_UNSTABLE) || (current_state == PREPARE_CALIBRATION_STABLE)) {
@@ -306,7 +306,7 @@ namespace sensor {
     if (timestep >= 2 && timestep <= 1800) {
       Serial.print(F("Setting Measurement Interval to : "));
       Serial.print(timestep);
-      Serial.println("s.");
+      Serial.println(F("s."));
       sensor::scd30.setMeasurementInterval(timestep);
       config::measurement_timestep = timestep;
       led_effects::showKITTWheel(color::green, 1);
@@ -318,7 +318,7 @@ namespace sensor {
       Serial.print(F("Force calibration, at "));
       config::co2_calibration_level = calibrationLevel;
       Serial.print(config::co2_calibration_level);
-      Serial.println(" ppm.");
+      Serial.println(F(" ppm."));
       sensor::startCalibrationProcess();
     }
   }