diff --git a/tests/domain/epc/test_main_heating_guard.py b/tests/domain/epc/test_main_heating_guard.py
index 452474d61..a32f3710f 100644
--- a/tests/domain/epc/test_main_heating_guard.py
+++ b/tests/domain/epc/test_main_heating_guard.py
@@ -19,6 +19,38 @@ def test_guard_resolves_high_heat_retention_storage() -> None:
     assert result is MainHeatingSystemType.ELECTRIC_STORAGE_HIGH_HEAT_RETENTION
 
 
+@pytest.mark.parametrize(
+    ("description", "expected"),
+    [
+        # The Gas CPSU dumping ground (ADR-0045): solid-fuel room heaters and
+        # electric ("NA" type) boilers the LLM sent to Gas CPSU (120, mains gas).
+        (
+            "Solid fuel room heaters: Open fire in grate",
+            MainHeatingSystemType.SOLID_FUEL_ROOM_HEATER_OPEN_FIRE,
+        ),
+        (
+            "Solid fuel room heaters: Open fire with back boiler (no radiators)",
+            MainHeatingSystemType.SOLID_FUEL_ROOM_HEATER_OPEN_FIRE_BACK_BOILER,
+        ),
+        (
+            "Solid fuel room heaters: Closed room heater with boiler (no radiators)",
+            MainHeatingSystemType.SOLID_FUEL_ROOM_HEATER_CLOSED_WITH_BOILER,
+        ),
+        # "NA" is the boiler-type value meaning "not a gas combi/regular/CPSU" —
+        # i.e. an electric boiler.
+        ("Boiler: A rated NA", MainHeatingSystemType.ELECTRIC_BOILER),
+    ],
+)
+def test_guard_resolves_the_gas_cpsu_dumping_ground(
+    description: str, expected: MainHeatingSystemType
+) -> None:
+    # Act
+    result = main_heating_guard(description)
+
+    # Assert
+    assert result is expected
+
+
 @pytest.mark.parametrize(
     "description",
     [
@@ -27,6 +59,12 @@ def test_guard_resolves_high_heat_retention_storage() -> None:
         "Electric Storage Systems: Old (large volume) storage heaters",
         "Electric Storage Systems: Modern (slimline) storage heaters",
         "Electric Storage Systems: Fan storage heaters",
+        # Genuinely-gas boilers the LLM already classifies correctly (not "NA").
+        "Boiler: A rated Combi",
+        "Boiler: C rated Regular Boiler",
+        # A plain closed room heater (no boiler) is the existing 633 archetype —
+        # the LLM keeps it; only "…with boiler" (634) is guarded.
+        "Solid fuel room heaters: Closed room heater (no boiler)",
         # Unrelated / varied phrasings are the LLM's job.
         "Gas boiler",
         "",