diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index 07299a3a5c..02766f8bec 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -48,6 +48,145 @@
 
 Temperature thermalManager;
 
+// public:
+
+int Temperature::current_temperature_raw[EXTRUDERS] = { 0 };
+float Temperature::current_temperature[EXTRUDERS] = { 0.0 };
+int Temperature::target_temperature[EXTRUDERS] = { 0 };
+
+int Temperature::current_temperature_bed_raw = 0;
+float Temperature::current_temperature_bed = 0.0;
+int Temperature::target_temperature_bed = 0;
+
+#if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
+  float Temperature::redundant_temperature = 0.0;
+#endif
+
+unsigned char Temperature::soft_pwm_bed;
+
+#if ENABLED(FAN_SOFT_PWM)
+  unsigned char Temperature::fanSpeedSoftPwm[FAN_COUNT];
+#endif
+
+#if ENABLED(PIDTEMP)
+  #if ENABLED(PID_PARAMS_PER_EXTRUDER)
+    float Temperature::Kp[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(DEFAULT_Kp),
+          Temperature::Ki[EXTRUDERS] = ARRAY_BY_EXTRUDERS1((DEFAULT_Ki) * (PID_dT)),
+          Temperature::Kd[EXTRUDERS] = ARRAY_BY_EXTRUDERS1((DEFAULT_Kd) / (PID_dT));
+    #if ENABLED(PID_ADD_EXTRUSION_RATE)
+      float Temperature::Kc[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(DEFAULT_Kc);
+    #endif
+  #else
+    float Temperature::Kp = DEFAULT_Kp,
+          Temperature::Ki = (DEFAULT_Ki) * (PID_dT),
+          Temperature::Kd = (DEFAULT_Kd) / (PID_dT);
+    #if ENABLED(PID_ADD_EXTRUSION_RATE)
+      float Temperature::Kc = DEFAULT_Kc;
+    #endif
+  #endif
+#endif
+
+#if ENABLED(PIDTEMPBED)
+  float Temperature::bedKp = DEFAULT_bedKp,
+        Temperature::bedKi = ((DEFAULT_bedKi) * PID_dT),
+        Temperature::bedKd = ((DEFAULT_bedKd) / PID_dT);
+#endif
+
+#if ENABLED(BABYSTEPPING)
+  volatile int Temperature::babystepsTodo[3] = { 0 };
+#endif
+
+#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
+  int Temperature::watch_target_temp[EXTRUDERS] = { 0 };
+  millis_t Temperature::watch_heater_next_ms[EXTRUDERS] = { 0 };
+#endif
+
+#if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_BED_TEMP_PERIOD > 0
+  int Temperature::watch_target_bed_temp = 0;
+  millis_t Temperature::watch_bed_next_ms = 0;
+#endif
+
+#if ENABLED(PREVENT_DANGEROUS_EXTRUDE)
+  float Temperature::extrude_min_temp = EXTRUDE_MINTEMP;
+#endif
+
+// private:
+
+#if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
+  int Temperature::redundant_temperature_raw = 0;
+  float Temperature::redundant_temperature = 0.0;
+#endif
+
+volatile bool Temperature::temp_meas_ready = false;
+
+#if ENABLED(PIDTEMP)
+  float Temperature::temp_iState[EXTRUDERS] = { 0 };
+  float Temperature::temp_dState[EXTRUDERS] = { 0 };
+  float Temperature::pTerm[EXTRUDERS];
+  float Temperature::iTerm[EXTRUDERS];
+  float Temperature::dTerm[EXTRUDERS];
+
+  #if ENABLED(PID_ADD_EXTRUSION_RATE)
+    float Temperature::cTerm[EXTRUDERS];
+    long Temperature::last_position[EXTRUDERS];
+    long Temperature::lpq[LPQ_MAX_LEN];
+    int Temperature::lpq_ptr = 0;
+  #endif
+
+  float Temperature::pid_error[EXTRUDERS];
+  float Temperature::temp_iState_min[EXTRUDERS];
+  float Temperature::temp_iState_max[EXTRUDERS];
+  bool Temperature::pid_reset[EXTRUDERS];
+#endif
+
+#if ENABLED(PIDTEMPBED)
+  float Temperature::temp_iState_bed = { 0 };
+  float Temperature::temp_dState_bed = { 0 };
+  float Temperature::pTerm_bed;
+  float Temperature::iTerm_bed;
+  float Temperature::dTerm_bed;
+  float Temperature::pid_error_bed;
+  float Temperature::temp_iState_min_bed;
+  float Temperature::temp_iState_max_bed;
+#else
+  millis_t Temperature::next_bed_check_ms;
+#endif
+
+unsigned long Temperature::raw_temp_value[4] = { 0 };
+unsigned long Temperature::raw_temp_bed_value = 0;
+
+// Init min and max temp with extreme values to prevent false errors during startup
+int Temperature::minttemp_raw[EXTRUDERS] = ARRAY_BY_EXTRUDERS(HEATER_0_RAW_LO_TEMP , HEATER_1_RAW_LO_TEMP , HEATER_2_RAW_LO_TEMP, HEATER_3_RAW_LO_TEMP);
+int Temperature::maxttemp_raw[EXTRUDERS] = ARRAY_BY_EXTRUDERS(HEATER_0_RAW_HI_TEMP , HEATER_1_RAW_HI_TEMP , HEATER_2_RAW_HI_TEMP, HEATER_3_RAW_HI_TEMP);
+int Temperature::minttemp[EXTRUDERS] = { 0 };
+int Temperature::maxttemp[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(16383);
+
+#ifdef BED_MINTEMP
+  int Temperature::bed_minttemp_raw = HEATER_BED_RAW_LO_TEMP;
+#endif
+
+#ifdef BED_MAXTEMP
+  int Temperature::bed_maxttemp_raw = HEATER_BED_RAW_HI_TEMP;
+#endif
+
+#if ENABLED(FILAMENT_WIDTH_SENSOR)
+  int Temperature::meas_shift_index;  // Index of a delayed sample in buffer
+#endif
+
+#if HAS_AUTO_FAN
+  millis_t Temperature::next_auto_fan_check_ms;
+#endif
+
+unsigned char Temperature::soft_pwm[EXTRUDERS];
+
+#if ENABLED(FAN_SOFT_PWM)
+  unsigned char Temperature::soft_pwm_fan[FAN_COUNT];
+#endif
+
+#if ENABLED(FILAMENT_WIDTH_SENSOR)
+  int Temperature::current_raw_filwidth = 0;  //Holds measured filament diameter - one extruder only
+#endif
+
 #if HAS_PID_HEATING
 
   void Temperature::PID_autotune(float temp, int extruder, int ncycles, bool set_result/*=false*/) {
@@ -283,31 +422,9 @@ Temperature thermalManager;
 
 #endif // HAS_PID_HEATING
 
-#if ENABLED(PIDTEMP)
-
-  #if ENABLED(PID_PARAMS_PER_EXTRUDER)
-
-    float Temperature::Kp[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(DEFAULT_Kp),
-          Temperature::Ki[EXTRUDERS] = ARRAY_BY_EXTRUDERS1((DEFAULT_Ki) * (PID_dT)),
-          Temperature::Kd[EXTRUDERS] = ARRAY_BY_EXTRUDERS1((DEFAULT_Kd) / (PID_dT));
-
-    #if ENABLED(PID_ADD_EXTRUSION_RATE)
-      float Temperature::Kc[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(DEFAULT_Kc);
-    #endif
-
-  #else
-
-    float Temperature::Kp = DEFAULT_Kp,
-          Temperature::Ki = (DEFAULT_Ki) * (PID_dT),
-          Temperature::Kd = (DEFAULT_Kd) / (PID_dT);
-
-    #if ENABLED(PID_ADD_EXTRUSION_RATE)
-      float Temperature::Kc = DEFAULT_Kc;
-    #endif
-
-  #endif
-
-#endif
+/**
+ * Class and Instance Methods
+ */
 
 Temperature::Temperature() { }
 
@@ -1045,7 +1162,17 @@ void Temperature::init() {
 
 #if ENABLED(THERMAL_PROTECTION_HOTENDS) || HAS_THERMALLY_PROTECTED_BED
 
-  void Temperature::thermal_runaway_protection(TRState* state, millis_t* timer, float temperature, float target_temperature, int heater_id, int period_seconds, int hysteresis_degc) {
+  #if ENABLED(THERMAL_PROTECTION_HOTENDS)
+    Temperature::TRState Temperature::thermal_runaway_state_machine[EXTRUDERS] = { TRInactive };
+    millis_t Temperature::thermal_runaway_timer[EXTRUDERS] = { 0 };
+  #endif
+
+  #if HAS_THERMALLY_PROTECTED_BED
+    Temperature::TRState Temperature::thermal_runaway_bed_state_machine = TRInactive;
+    millis_t Temperature::thermal_runaway_bed_timer;
+  #endif
+
+  void Temperature::thermal_runaway_protection(Temperature::TRState* state, millis_t* timer, float temperature, float target_temperature, int heater_id, int period_seconds, int hysteresis_degc) {
 
     static float tr_target_temperature[EXTRUDERS + 1] = { 0.0 };
 
@@ -1242,7 +1369,7 @@ void Temperature::set_current_temp_raw() {
  *  - Check new temperature values for MIN/MAX errors
  *  - Step the babysteps value for each axis towards 0
  */
-ISR(TIMER0_COMPB_vect) { thermalManager.isr(); }
+ISR(TIMER0_COMPB_vect) { Temperature::isr(); }
 
 void Temperature::isr() {
 
diff --git a/Marlin/temperature.h b/Marlin/temperature.h
index 1e9276a804..cb57107578 100644
--- a/Marlin/temperature.h
+++ b/Marlin/temperature.h
@@ -42,22 +42,22 @@ class Temperature {
 
   public:
 
-    int current_temperature_raw[EXTRUDERS] = { 0 };
-    float current_temperature[EXTRUDERS] = { 0.0 };
-    int target_temperature[EXTRUDERS] = { 0 };
+    static int current_temperature_raw[EXTRUDERS];
+    static float current_temperature[EXTRUDERS];
+    static int target_temperature[EXTRUDERS];
 
-    int current_temperature_bed_raw = 0;
-    float current_temperature_bed = 0.0;
-    int target_temperature_bed = 0;
+    static int current_temperature_bed_raw;
+    static float current_temperature_bed;
+    static int target_temperature_bed;
 
     #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-      float redundant_temperature = 0.0;
+      static float redundant_temperature;
     #endif
 
-    unsigned char soft_pwm_bed;
+    static unsigned char soft_pwm_bed;
 
     #if ENABLED(FAN_SOFT_PWM)
-      unsigned char fanSpeedSoftPwm[FAN_COUNT];
+      static unsigned char fanSpeedSoftPwm[FAN_COUNT];
     #endif
 
     #if ENABLED(PIDTEMP) || ENABLED(PIDTEMPBED)
@@ -70,7 +70,7 @@ class Temperature {
 
         static float Kp[EXTRUDERS], Ki[EXTRUDERS], Kd[EXTRUDERS];
         #if ENABLED(PID_ADD_EXTRUSION_RATE)
-          float Kc[EXTRUDERS];
+          static float Kc[EXTRUDERS];
         #endif
         #define PID_PARAM(param, e) Temperature::param[e]
 
@@ -93,117 +93,109 @@ class Temperature {
     #endif
 
     #if ENABLED(PIDTEMPBED)
-      float bedKp = DEFAULT_bedKp,
-            bedKi = ((DEFAULT_bedKi) * PID_dT),
-            bedKd = ((DEFAULT_bedKd) / PID_dT);
+      static float bedKp, bedKi, bedKd;
     #endif
 
     #if ENABLED(BABYSTEPPING)
-      volatile int babystepsTodo[3] = { 0 };
+      static volatile int babystepsTodo[3];
     #endif
 
     #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
-      int watch_target_temp[EXTRUDERS] = { 0 };
-      millis_t watch_heater_next_ms[EXTRUDERS] = { 0 };
+      static int watch_target_temp[EXTRUDERS];
+      static millis_t watch_heater_next_ms[EXTRUDERS];
     #endif
 
     #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_BED_TEMP_PERIOD > 0
-      int watch_target_bed_temp = 0;
-      millis_t watch_bed_next_ms = 0;
+      static int watch_target_bed_temp;
+      static millis_t watch_bed_next_ms;
     #endif
 
     #if ENABLED(PREVENT_DANGEROUS_EXTRUDE)
-      float extrude_min_temp = EXTRUDE_MINTEMP;
-      FORCE_INLINE bool tooColdToExtrude(uint8_t e) { return degHotend(e) < extrude_min_temp; }
+      static float extrude_min_temp;
+      static bool tooColdToExtrude(uint8_t e) { return degHotend(e) < extrude_min_temp; }
     #else
-      FORCE_INLINE bool tooColdToExtrude(uint8_t e) { UNUSED(e); return false; }
+      static bool tooColdToExtrude(uint8_t e) { UNUSED(e); return false; }
     #endif
 
   private:
 
     #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-      int redundant_temperature_raw = 0;
-      float redundant_temperature = 0.0;
+      static int redundant_temperature_raw;
+      static float redundant_temperature;
     #endif
 
-    volatile bool temp_meas_ready = false;
+    static volatile bool temp_meas_ready;
 
     #if ENABLED(PIDTEMP)
-      float temp_iState[EXTRUDERS] = { 0 };
-      float temp_dState[EXTRUDERS] = { 0 };
-      float pTerm[EXTRUDERS];
-      float iTerm[EXTRUDERS];
-      float dTerm[EXTRUDERS];
+      static float temp_iState[EXTRUDERS];
+      static float temp_dState[EXTRUDERS];
+      static float pTerm[EXTRUDERS];
+      static float iTerm[EXTRUDERS];
+      static float dTerm[EXTRUDERS];
 
       #if ENABLED(PID_ADD_EXTRUSION_RATE)
-        float cTerm[EXTRUDERS];
-        long last_position[EXTRUDERS];
-        long lpq[LPQ_MAX_LEN];
-        int lpq_ptr = 0;
+        static float cTerm[EXTRUDERS];
+        static long last_position[EXTRUDERS];
+        static long lpq[LPQ_MAX_LEN];
+        static int lpq_ptr;
       #endif
 
-      float pid_error[EXTRUDERS];
-      float temp_iState_min[EXTRUDERS];
-      float temp_iState_max[EXTRUDERS];
-      bool pid_reset[EXTRUDERS];
+      static float pid_error[EXTRUDERS];
+      static float temp_iState_min[EXTRUDERS];
+      static float temp_iState_max[EXTRUDERS];
+      static bool pid_reset[EXTRUDERS];
     #endif
 
     #if ENABLED(PIDTEMPBED)
-      float temp_iState_bed = { 0 };
-      float temp_dState_bed = { 0 };
-      float pTerm_bed;
-      float iTerm_bed;
-      float dTerm_bed;
-      float pid_error_bed;
-      float temp_iState_min_bed;
-      float temp_iState_max_bed;
+      static float temp_iState_bed;
+      static float temp_dState_bed;
+      static float pTerm_bed;
+      static float iTerm_bed;
+      static float dTerm_bed;
+      static float pid_error_bed;
+      static float temp_iState_min_bed;
+      static float temp_iState_max_bed;
     #else
-      millis_t next_bed_check_ms;
+      static millis_t next_bed_check_ms;
     #endif
 
-    unsigned long raw_temp_value[4] = { 0 };
-    unsigned long raw_temp_bed_value = 0;
+    static unsigned long raw_temp_value[4];
+    static unsigned long raw_temp_bed_value;
 
     // Init min and max temp with extreme values to prevent false errors during startup
-    int minttemp_raw[EXTRUDERS] = ARRAY_BY_EXTRUDERS(HEATER_0_RAW_LO_TEMP , HEATER_1_RAW_LO_TEMP , HEATER_2_RAW_LO_TEMP, HEATER_3_RAW_LO_TEMP);
-    int maxttemp_raw[EXTRUDERS] = ARRAY_BY_EXTRUDERS(HEATER_0_RAW_HI_TEMP , HEATER_1_RAW_HI_TEMP , HEATER_2_RAW_HI_TEMP, HEATER_3_RAW_HI_TEMP);
-    int minttemp[EXTRUDERS] = { 0 };
-    int maxttemp[EXTRUDERS] = ARRAY_BY_EXTRUDERS1(16383);
+    static int minttemp_raw[EXTRUDERS];
+    static int maxttemp_raw[EXTRUDERS];
+    static int minttemp[EXTRUDERS];
+    static int maxttemp[EXTRUDERS];
 
     #ifdef BED_MINTEMP
-      int bed_minttemp_raw = HEATER_BED_RAW_LO_TEMP;
+      static int bed_minttemp_raw;
     #endif
 
     #ifdef BED_MAXTEMP
-      int bed_maxttemp_raw = HEATER_BED_RAW_HI_TEMP;
+      static int bed_maxttemp_raw;
     #endif
 
     #if ENABLED(FILAMENT_WIDTH_SENSOR)
-      int meas_shift_index;  // Index of a delayed sample in buffer
+      static int meas_shift_index;  // Index of a delayed sample in buffer
     #endif
 
     #if HAS_AUTO_FAN
-      millis_t next_auto_fan_check_ms;
+      static millis_t next_auto_fan_check_ms;
     #endif
 
-    unsigned char soft_pwm[EXTRUDERS];
+    static unsigned char soft_pwm[EXTRUDERS];
 
     #if ENABLED(FAN_SOFT_PWM)
-      unsigned char soft_pwm_fan[FAN_COUNT];
+      static unsigned char soft_pwm_fan[FAN_COUNT];
     #endif
 
     #if ENABLED(FILAMENT_WIDTH_SENSOR)
-      int current_raw_filwidth = 0;  //Holds measured filament diameter - one extruder only
+      static int current_raw_filwidth;  //Holds measured filament diameter - one extruder only
     #endif
 
   public:
 
-    /**
-     * Static (class) methods
-     */
-    static float analog2temp(int raw, uint8_t e);
-    static float analog2tempBed(int raw);
-
     /**
      * Instance Methods
      */
@@ -212,19 +204,25 @@ class Temperature {
 
     void init();
 
+    /**
+     * Static (class) methods
+     */
+    static float analog2temp(int raw, uint8_t e);
+    static float analog2tempBed(int raw);
+
     /**
      * Called from the Temperature ISR
      */
-    void isr();
+    static void isr();
 
     /**
      * Call periodically to manage heaters
      */
-    void manage_heater();
+    static void manage_heater();
 
     #if ENABLED(FILAMENT_WIDTH_SENSOR)
-      float analog2widthFil(); // Convert raw Filament Width to millimeters
-      int widthFil_to_size_ratio(); // Convert raw Filament Width to an extrusion ratio
+      static float analog2widthFil(); // Convert raw Filament Width to millimeters
+      static int widthFil_to_size_ratio(); // Convert raw Filament Width to an extrusion ratio
     #endif
 
 
@@ -232,68 +230,68 @@ class Temperature {
     //inline so that there is no performance decrease.
     //deg=degreeCelsius
 
-    FORCE_INLINE float degHotend(uint8_t extruder) { return current_temperature[extruder]; }
-    FORCE_INLINE float degBed() { return current_temperature_bed; }
+    static float degHotend(uint8_t extruder) { return current_temperature[extruder]; }
+    static float degBed() { return current_temperature_bed; }
 
     #if ENABLED(SHOW_TEMP_ADC_VALUES)
-    FORCE_INLINE float rawHotendTemp(uint8_t extruder) { return current_temperature_raw[extruder]; }
-    FORCE_INLINE float rawBedTemp() { return current_temperature_bed_raw; }
+    static float rawHotendTemp(uint8_t extruder) { return current_temperature_raw[extruder]; }
+    static float rawBedTemp() { return current_temperature_bed_raw; }
     #endif
 
-    FORCE_INLINE float degTargetHotend(uint8_t extruder) { return target_temperature[extruder]; }
-    FORCE_INLINE float degTargetBed() { return target_temperature_bed; }
+    static float degTargetHotend(uint8_t extruder) { return target_temperature[extruder]; }
+    static float degTargetBed() { return target_temperature_bed; }
 
     #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
-      void start_watching_heater(int e = 0);
+      static void start_watching_heater(int e = 0);
     #endif
 
     #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
-      void start_watching_bed();
+      static void start_watching_bed();
     #endif
 
-    FORCE_INLINE void setTargetHotend(const float& celsius, uint8_t extruder) {
+    static void setTargetHotend(const float& celsius, uint8_t extruder) {
       target_temperature[extruder] = celsius;
       #if ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0
         start_watching_heater(extruder);
       #endif
     }
 
-    FORCE_INLINE void setTargetBed(const float& celsius) {
+    static void setTargetBed(const float& celsius) {
       target_temperature_bed = celsius;
       #if ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0
         start_watching_bed();
       #endif
     }
 
-    FORCE_INLINE bool isHeatingHotend(uint8_t extruder) { return target_temperature[extruder] > current_temperature[extruder]; }
-    FORCE_INLINE bool isHeatingBed() { return target_temperature_bed > current_temperature_bed; }
+    static bool isHeatingHotend(uint8_t extruder) { return target_temperature[extruder] > current_temperature[extruder]; }
+    static bool isHeatingBed() { return target_temperature_bed > current_temperature_bed; }
 
-    FORCE_INLINE bool isCoolingHotend(uint8_t extruder) { return target_temperature[extruder] < current_temperature[extruder]; }
-    FORCE_INLINE bool isCoolingBed() { return target_temperature_bed < current_temperature_bed; }
+    static bool isCoolingHotend(uint8_t extruder) { return target_temperature[extruder] < current_temperature[extruder]; }
+    static bool isCoolingBed() { return target_temperature_bed < current_temperature_bed; }
 
     /**
      * The software PWM power for a heater
      */
-    int getHeaterPower(int heater);
+    static int getHeaterPower(int heater);
 
     /**
      * Switch off all heaters, set all target temperatures to 0
      */
-    void disable_all_heaters();
+    static void disable_all_heaters();
 
     /**
      * Perform auto-tuning for hotend or bed in response to M303
      */
     #if HAS_PID_HEATING
-      void PID_autotune(float temp, int extruder, int ncycles, bool set_result=false);
+      static void PID_autotune(float temp, int extruder, int ncycles, bool set_result=false);
     #endif
 
     /**
      * Update the temp manager when PID values change
      */
-    void updatePID();
+    static void updatePID();
 
-    FORCE_INLINE void autotempShutdown() {
+    static void autotempShutdown() {
       #if ENABLED(AUTOTEMP)
         if (planner.autotemp_enabled) {
           planner.autotemp_enabled = false;
@@ -305,7 +303,7 @@ class Temperature {
 
     #if ENABLED(BABYSTEPPING)
 
-      FORCE_INLINE void babystep_axis(AxisEnum axis, int distance) {
+      static void babystep_axis(AxisEnum axis, int distance) {
         #if ENABLED(COREXY) || ENABLED(COREXZ) || ENABLED(COREYZ)
           #if ENABLED(BABYSTEP_XY)
             switch (axis) {
@@ -337,40 +335,40 @@ class Temperature {
 
   private:
 
-    void set_current_temp_raw();
+    static void set_current_temp_raw();
 
-    void updateTemperaturesFromRawValues();
+    static void updateTemperaturesFromRawValues();
 
     #if ENABLED(HEATER_0_USES_MAX6675)
-      int read_max6675();
+      static int read_max6675();
     #endif
 
-    void checkExtruderAutoFans();
+    static void checkExtruderAutoFans();
 
-    float get_pid_output(int e);
+    static float get_pid_output(int e);
 
     #if ENABLED(PIDTEMPBED)
-      float get_pid_output_bed();
+      static float get_pid_output_bed();
     #endif
 
-    void _temp_error(int e, const char* serial_msg, const char* lcd_msg);
-    void min_temp_error(uint8_t e);
-    void max_temp_error(uint8_t e);
+    static void _temp_error(int e, const char* serial_msg, const char* lcd_msg);
+    static void min_temp_error(uint8_t e);
+    static void max_temp_error(uint8_t e);
 
     #if ENABLED(THERMAL_PROTECTION_HOTENDS) || HAS_THERMALLY_PROTECTED_BED
 
       typedef enum TRState { TRInactive, TRFirstHeating, TRStable, TRRunaway } TRstate;
 
-      void thermal_runaway_protection(TRState* state, millis_t* timer, float temperature, float target_temperature, int heater_id, int period_seconds, int hysteresis_degc);
+      static void thermal_runaway_protection(TRState* state, millis_t* timer, float temperature, float target_temperature, int heater_id, int period_seconds, int hysteresis_degc);
 
       #if ENABLED(THERMAL_PROTECTION_HOTENDS)
-        TRState thermal_runaway_state_machine[EXTRUDERS] = { TRInactive };
-        millis_t thermal_runaway_timer[EXTRUDERS] = { 0 };
+        static TRState thermal_runaway_state_machine[EXTRUDERS];
+        static millis_t thermal_runaway_timer[EXTRUDERS];
       #endif
 
       #if HAS_THERMALLY_PROTECTED_BED
-        TRState thermal_runaway_bed_state_machine = TRInactive;
-        millis_t thermal_runaway_bed_timer;
+        static TRState thermal_runaway_bed_state_machine;
+        static millis_t thermal_runaway_bed_timer;
       #endif
 
     #endif // THERMAL_PROTECTION