Index: sources/drydemo/StateControllerHDFTreatment.cpp
===================================================================
diff -u -r521f29cb7dcd0de352dd744292488380e07cb9e3 -re8edefcae8e47854198b06c1a65e4e45da5f3afc
--- sources/drydemo/StateControllerHDFTreatment.cpp	(.../StateControllerHDFTreatment.cpp)	(revision 521f29cb7dcd0de352dd744292488380e07cb9e3)
+++ sources/drydemo/StateControllerHDFTreatment.cpp	(.../StateControllerHDFTreatment.cpp)	(revision e8edefcae8e47854198b06c1a65e4e45da5f3afc)
@@ -13,6 +13,7 @@
     _treatmentHDFVars.hdfControlTimeCtr           = 0;
     _treatmentHDFVars.hdfHasMaxVolumeBeenReached  = false;
     _treatmentHDFVars.hdfIsRequested              = true;
+    _treatmentHDFVars.hdfPrevIsRequested          = true;
 }
 
 float StateController::handleHDFCheckRate(const float proposedRateMLPM, const bool initRate)
@@ -107,8 +108,10 @@
     newHDFDilution                               = extractU32DataFromReceivedMessage(ID_UI_HDF_ADJUSTMENT_RQST, HDF_ADJ_MSG_DILUTION_INDEX);
     _treatmentParams.hdfSubstitutionFluidVolumeL = extractF32DataFromReceivedMessage(ID_UI_HDF_ADJUSTMENT_RQST, HDF_ADJ_MSG_FLUID_VOL_INDEX);
 
-    // Trigger the submode change if the dilution mode has changed
-    if (_treatmentParams.hdfDilution != newHDFDilution) { triggerAnAlarm(ALARM_ID_TD_HDF_SUBMODE_CHANGE); }
+    // Trigger the submode change if the dilution mode has changed. Set HDF to pause until the alarm is cleared
+    if (_treatmentParams.hdfDilution != newHDFDilution) {
+        triggerAnAlarm(ALARM_ID_TD_HDF_SUBMODE_CHANGE);
+    }
 
     _treatmentParams.hdfDilution = newHDFDilution;
     acceptReject                 = ACCEPT_VALUE;