diff --git a/homeassistant/components/number/const.py b/homeassistant/components/number/const.py
index f29206df7c5..9824d736fe9 100644
--- a/homeassistant/components/number/const.py
+++ b/homeassistant/components/number/const.py
@@ -124,7 +124,7 @@ class NumberDeviceClass(StrEnum):
     CO = "carbon_monoxide"
     """Carbon Monoxide gas concentration.
 
-    Unit of measurement: `ppm` (parts per million), `mg/m³`
+    Unit of measurement: `ppm` (parts per million), `mg/m³`, `μg/m³`
     """
 
     CO2 = "carbon_dioxide"
@@ -478,6 +478,7 @@ DEVICE_CLASS_UNITS: dict[NumberDeviceClass, set[type[StrEnum] | str | None]] = {
     NumberDeviceClass.CO: {
         CONCENTRATION_PARTS_PER_MILLION,
         CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+        CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
     },
     NumberDeviceClass.CO2: {CONCENTRATION_PARTS_PER_MILLION},
     NumberDeviceClass.CONDUCTIVITY: set(UnitOfConductivity),
diff --git a/homeassistant/components/sensor/const.py b/homeassistant/components/sensor/const.py
index b91bd26d410..356d2313c31 100644
--- a/homeassistant/components/sensor/const.py
+++ b/homeassistant/components/sensor/const.py
@@ -157,7 +157,7 @@ class SensorDeviceClass(StrEnum):
     CO = "carbon_monoxide"
     """Carbon Monoxide gas concentration.
 
-    Unit of measurement: `ppm` (parts per million), `mg/m³`
+    Unit of measurement: `ppm` (parts per million), `mg/m³`, `μg/m³`
     """
 
     CO2 = "carbon_dioxide"
@@ -589,6 +589,7 @@ DEVICE_CLASS_UNITS: dict[SensorDeviceClass, set[type[StrEnum] | str | None]] = {
     SensorDeviceClass.CO: {
         CONCENTRATION_PARTS_PER_MILLION,
         CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+        CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
     },
     SensorDeviceClass.CO2: {CONCENTRATION_PARTS_PER_MILLION},
     SensorDeviceClass.CONDUCTIVITY: set(UnitOfConductivity),
diff --git a/homeassistant/util/unit_conversion.py b/homeassistant/util/unit_conversion.py
index 322410f61ec..d57913ee397 100644
--- a/homeassistant/util/unit_conversion.py
+++ b/homeassistant/util/unit_conversion.py
@@ -191,10 +191,14 @@ class CarbonMonoxideConcentrationConverter(BaseUnitConverter):
         CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER: (
             _CARBON_MONOXIDE_MOLAR_MASS / _AMBIENT_IDEAL_GAS_MOLAR_VOLUME * 1e3
         ),
+        CONCENTRATION_MICROGRAMS_PER_CUBIC_METER: (
+            _CARBON_MONOXIDE_MOLAR_MASS / _AMBIENT_IDEAL_GAS_MOLAR_VOLUME * 1e6
+        ),
     }
     VALID_UNITS = {
         CONCENTRATION_PARTS_PER_MILLION,
         CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+        CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
     }
 
 
diff --git a/tests/util/test_unit_conversion.py b/tests/util/test_unit_conversion.py
index 824d9708f7f..ba4926eba6d 100644
--- a/tests/util/test_unit_conversion.py
+++ b/tests/util/test_unit_conversion.py
@@ -288,18 +288,45 @@ _CONVERTED_VALUE: dict[
         ),
     ],
     CarbonMonoxideConcentrationConverter: [
+        # PPM to other units
         (
             1,
             CONCENTRATION_PARTS_PER_MILLION,
             1.16441,
             CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
         ),
+        (
+            1,
+            CONCENTRATION_PARTS_PER_MILLION,
+            1164.41,
+            CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
+        ),
+        # MILLIGRAMS_PER_CUBIC_METER to other units
         (
             120,
             CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
             103.05655,
             CONCENTRATION_PARTS_PER_MILLION,
         ),
+        (
+            120,
+            CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+            120000,
+            CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
+        ),
+        # MICROGRAMS_PER_CUBIC_METER to other units
+        (
+            120000,
+            CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
+            103.05655,
+            CONCENTRATION_PARTS_PER_MILLION,
+        ),
+        (
+            120000,
+            CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
+            120,
+            CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
+        ),
     ],
     ConductivityConverter: [
         (