diff --git a/Source/hvac.f90 b/Source/hvac.f90
index 382fb280af4..46a019b3795 100644
--- a/Source/hvac.f90
+++ b/Source/hvac.f90
@@ -429,6 +429,16 @@ SUBROUTINE READ_HVAC
             WRITE(MESSAGE,'(A,I5)') 'ERROR(513): Ductnode has no ID, HVAC line number:',NN
             CALL SHUTDOWN(MESSAGE); RETURN
          ENDIF
+         IF ((GEOM .OR. GEOM2) .AND. VENT_ID/='null') THEN
+            WRITE(MESSAGE,'(A,A,A,I5)') 'ERROR(yyy): Ductnode with GEOM cannot have a VENT_ID. Ductnode ID:',TRIM(DN%ID),&
+                                        ', HVAC line number:',NN
+            CALL SHUTDOWN(MESSAGE); RETURN
+         ENDIF
+         IF (.NOT. GEOM .AND. VENT_ID=='null') THEN
+            WRITE(MESSAGE,'(A,A,A,I5)') 'ERROR(yyy): Ductnode with needs either GEOM or VENT_ID. Ductnode ID:',TRIM(DN%ID),&
+                                        ', HVAC line number:',NN
+            CALL SHUTDOWN(MESSAGE); RETURN
+         ENDIF
          DN%VENT_ID = VENT_ID
          DN%GEOM = GEOM
          IF (DN%VENT .AND. DN%GEOM) THEN
@@ -457,12 +467,12 @@ SUBROUTINE READ_HVAC
             DN%N_DUCTS=ND
          ENDDO
          IF (DN%N_DUCTS == 1 .AND. .NOT. GEOM .AND. .NOT. AMBIENT .AND. VENT_ID=='null') THEN
-            WRITE(MESSAGE,'(A,A,A,I5)') 'ERROR(515): Non-AMBIENT or non VENT-connected ductnode must have >=2 ducts. Ductnode ID:',&
-                                        TRIM(DN%ID),', HVAC line number:',NN
+            WRITE(MESSAGE,'(A,A,A,A,I5)') 'ERROR(515): Non-AMBIENT, non-VENT, and non-GEOM connected ductnode ',&
+               '(i.e., internal node) must have >=2 ducts. Ductnode ID:',TRIM(DN%ID),', HVAC line number:',NN
             CALL SHUTDOWN(MESSAGE); RETURN
          ENDIF
          IF (DN%N_DUCTS >= 2 .AND. (AMBIENT .OR. GEOM .OR. VENT_ID/='null')) THEN
-            WRITE(MESSAGE,'(A,A,A,I5)') 'ERROR(516): AMBIENT, GEOM, or VENT-connected ductnode must have 1 duct. Ductnode ID:',&
+            WRITE(MESSAGE,'(A,A,A,I5)') 'ERROR(516): AMBIENT, VENT, or GEOM-connected ductnode must have 1 duct. Ductnode ID:',&
                                         TRIM(DN%ID),', HVAC line number:',NN
             CALL SHUTDOWN(MESSAGE); RETURN
          ENDIF
diff --git a/Source/read.f90 b/Source/read.f90
index f79791e0ef5..085ddd5e166 100644
--- a/Source/read.f90
+++ b/Source/read.f90
@@ -11942,6 +11942,10 @@ SUBROUTINE READ_VENT
          WRITE(MESSAGE,'(3A)') 'ERROR(802): VENT ',TRIM(ID), ' needs an explicit ID because it involves HVAC.'
          CALL SHUTDOWN(MESSAGE,PROCESS_0_ONLY=.FALSE.) ; RETURN
       ENDIF
+      IF (SURF_ID=='HVAC' .AND. GEOM) THEN
+         WRITE(MESSAGE,'(3A)') 'ERROR(xxx): VENT ',TRIM(ID), ' cannot have SURF_ID=HVAC and GEOM=T.'
+         CALL SHUTDOWN(MESSAGE,PROCESS_0_ONLY=.FALSE.) ; RETURN
+      ENDIF
 
       ! Special cases where VENT is specified with PBX, PBY, PBZ, MB, or DB