Index: firmware/App/Modes/ModeStandby.c
===================================================================
diff -u -r4cc579577062113856fd266cb65b1ccbe33bb596 -rd0e6b55d2fed933caec5ca8f5b8f19c7f4d7ecea
--- firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision 4cc579577062113856fd266cb65b1ccbe33bb596)
+++ firmware/App/Modes/ModeStandby.c	(.../ModeStandby.c)	(revision d0e6b55d2fed933caec5ca8f5b8f19c7f4d7ecea)
@@ -49,6 +49,7 @@
 #define DISINFECTS_DATA_PUB_INTERVAL          ( 1 * MS_PER_SECOND / TASK_GENERAL_INTERVAL )    ///< Disinfects data publish interval in counts.
 #define DISINFECTS_TIME_INTERVAL_S            ( 2 * SECONDS_IN_A_DAY )                         ///< HD/DG 2-day service interval in seconds.
 #define FLUSH_TIME_INTERVAL_S                 ( 30 * SEC_PER_MIN * MS_PER_SECOND )             ///< Flush time interval in seconds.
+#define MAX_ALLOWED_RO_FILTER_TEMP_FOR_TX_C   44.0F                                            ///< Maximum allowed temperature to start a treatment in C.
 
 // ********** private data **********
 
@@ -310,6 +311,11 @@
         {
             rejReason = REQUEST_REJECT_REASON_DG_DISINFECT_HAS_BEEN_EXPIRED;
         }
+
+        if ( getHeatDisinfectTemperatureSensorValue() > MAX_ALLOWED_RO_FILTER_TEMP_FOR_TX_C )
+        {
+            rejReason = REQUEST_REJECT_REASON_DG_RO_FILTER_TEMPERATURE_OUT_OF_RANGE;
+        }
     }
 
     if ( REQUEST_REJECT_REASON_NONE == rejReason )