Add mg/m³ as a valid UOM for sensor/number Carbon Monoxide device class (#152456)

tests/util/test_unit_conversion.py

@@ -44,6 +44,7 @@ from homeassistant.util.unit_conversion import (
     AreaConverter,
     BaseUnitConverter,
     BloodGlucoseConcentrationConverter,
+    CarbonMonoxideConcentrationConverter,
     ConductivityConverter,
     DataRateConverter,
     DistanceConverter,
@@ -78,6 +79,7 @@ _ALL_CONVERTERS: dict[type[BaseUnitConverter], list[str | None]] = {
         AreaConverter,
         BloodGlucoseConcentrationConverter,
         MassVolumeConcentrationConverter,
+        CarbonMonoxideConcentrationConverter,
         ConductivityConverter,
         DataRateConverter,
         DistanceConverter,
@@ -114,6 +116,11 @@ _GET_UNIT_RATIO: dict[type[BaseUnitConverter], tuple[str | None, str | None, flo
         UnitOfBloodGlucoseConcentration.MILLIMOLE_PER_LITER,
         18,
     ),
+    CarbonMonoxideConcentrationConverter: (
+        CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+        CONCENTRATION_PARTS_PER_MILLION,
+        1.145609,
+    ),
     ConductivityConverter: (
         UnitOfConductivity.MICROSIEMENS_PER_CM,
         UnitOfConductivity.MILLISIEMENS_PER_CM,
@@ -280,6 +287,20 @@ _CONVERTED_VALUE: dict[
             UnitOfBloodGlucoseConcentration.MILLIGRAMS_PER_DECILITER,
         ),
     ],
+    CarbonMonoxideConcentrationConverter: [
+        (
+            1,
+            CONCENTRATION_PARTS_PER_MILLION,
+            1.145609,
+            CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+        ),
+        (
+            120,
+            CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+            104.74778,
+            CONCENTRATION_PARTS_PER_MILLION,
+        ),
+    ],
     ConductivityConverter: [
         # Deprecated to deprecated
         (5, UnitOfConductivity.SIEMENS, 5e3, UnitOfConductivity.MILLISIEMENS),