diff --git a/homeassistant/components/homekit_controller/const.py b/homeassistant/components/homekit_controller/const.py
index 924d27218a2..6aa5dc93662 100644
--- a/homeassistant/components/homekit_controller/const.py
+++ b/homeassistant/components/homekit_controller/const.py
@@ -21,6 +21,7 @@ HOMEKIT_ACCESSORY_DISPATCH = {
     "lock-mechanism": "lock",
     "contact": "binary_sensor",
     "motion": "binary_sensor",
+    "carbon-dioxide": "sensor",
     "humidity": "sensor",
     "light": "sensor",
     "temperature": "sensor",
diff --git a/homeassistant/components/homekit_controller/sensor.py b/homeassistant/components/homekit_controller/sensor.py
index 16109f08c10..596b697bede 100644
--- a/homeassistant/components/homekit_controller/sensor.py
+++ b/homeassistant/components/homekit_controller/sensor.py
@@ -1,4 +1,6 @@
 """Support for Homekit sensors."""
+from homekit.model.characteristics import CharacteristicsTypes
+
 from homeassistant.const import TEMP_CELSIUS
 
 from . import KNOWN_DEVICES, HomeKitEntity
@@ -6,39 +8,11 @@ from . import KNOWN_DEVICES, HomeKitEntity
 HUMIDITY_ICON = "mdi:water-percent"
 TEMP_C_ICON = "mdi:thermometer"
 BRIGHTNESS_ICON = "mdi:brightness-6"
+CO2_ICON = "mdi:periodic-table-co2"
 
 UNIT_PERCENT = "%"
 UNIT_LUX = "lux"
-
-
-async def async_setup_platform(hass, config, async_add_entities, discovery_info=None):
-    """Legacy set up platform."""
-    pass
-
-
-async def async_setup_entry(hass, config_entry, async_add_entities):
-    """Set up Homekit covers."""
-    hkid = config_entry.data["AccessoryPairingID"]
-    conn = hass.data[KNOWN_DEVICES][hkid]
-
-    def async_add_service(aid, service):
-        devtype = service["stype"]
-        info = {"aid": aid, "iid": service["iid"]}
-        if devtype == "humidity":
-            async_add_entities([HomeKitHumiditySensor(conn, info)], True)
-            return True
-
-        if devtype == "temperature":
-            async_add_entities([HomeKitTemperatureSensor(conn, info)], True)
-            return True
-
-        if devtype == "light":
-            async_add_entities([HomeKitLightSensor(conn, info)], True)
-            return True
-
-        return False
-
-    conn.add_listener(async_add_service)
+UNIT_CO2 = "ppm"
 
 
 class HomeKitHumiditySensor(HomeKitEntity):
@@ -51,9 +25,6 @@ class HomeKitHumiditySensor(HomeKitEntity):
 
     def get_characteristic_types(self):
         """Define the homekit characteristics the entity is tracking."""
-        # pylint: disable=import-error
-        from homekit.model.characteristics import CharacteristicsTypes
-
         return [CharacteristicsTypes.RELATIVE_HUMIDITY_CURRENT]
 
     @property
@@ -90,9 +61,6 @@ class HomeKitTemperatureSensor(HomeKitEntity):
 
     def get_characteristic_types(self):
         """Define the homekit characteristics the entity is tracking."""
-        # pylint: disable=import-error
-        from homekit.model.characteristics import CharacteristicsTypes
-
         return [CharacteristicsTypes.TEMPERATURE_CURRENT]
 
     @property
@@ -129,9 +97,6 @@ class HomeKitLightSensor(HomeKitEntity):
 
     def get_characteristic_types(self):
         """Define the homekit characteristics the entity is tracking."""
-        # pylint: disable=import-error
-        from homekit.model.characteristics import CharacteristicsTypes
-
         return [CharacteristicsTypes.LIGHT_LEVEL_CURRENT]
 
     @property
@@ -156,3 +121,68 @@ class HomeKitLightSensor(HomeKitEntity):
     def state(self):
         """Return the current light level in lux."""
         return self._state
+
+
+class HomeKitCarbonDioxideSensor(HomeKitEntity):
+    """Representation of a Homekit Carbon Dioxide sensor."""
+
+    def __init__(self, *args):
+        """Initialise the entity."""
+        super().__init__(*args)
+        self._state = None
+
+    def get_characteristic_types(self):
+        """Define the homekit characteristics the entity is tracking."""
+        return [CharacteristicsTypes.CARBON_DIOXIDE_LEVEL]
+
+    @property
+    def name(self):
+        """Return the name of the device."""
+        return "{} {}".format(super().name, "CO2")
+
+    @property
+    def icon(self):
+        """Return the sensor icon."""
+        return CO2_ICON
+
+    @property
+    def unit_of_measurement(self):
+        """Return units for the sensor."""
+        return UNIT_CO2
+
+    def _update_carbon_dioxide_level(self, value):
+        self._state = value
+
+    @property
+    def state(self):
+        """Return the current CO2 level in ppm."""
+        return self._state
+
+
+ENTITY_TYPES = {
+    "humidity": HomeKitHumiditySensor,
+    "temperature": HomeKitTemperatureSensor,
+    "light": HomeKitLightSensor,
+    "carbon-dioxide": HomeKitCarbonDioxideSensor,
+}
+
+
+async def async_setup_platform(hass, config, async_add_entities, discovery_info=None):
+    """Legacy set up platform."""
+    pass
+
+
+async def async_setup_entry(hass, config_entry, async_add_entities):
+    """Set up Homekit sensors."""
+    hkid = config_entry.data["AccessoryPairingID"]
+    conn = hass.data[KNOWN_DEVICES][hkid]
+
+    def async_add_service(aid, service):
+        entity_class = ENTITY_TYPES.get(service["stype"])
+        if not entity_class:
+            return False
+        info = {"aid": aid, "iid": service["iid"]}
+        async_add_entities([entity_class(conn, info)], True)
+        return True
+
+    conn.add_listener(async_add_service)
diff --git a/tests/components/homekit_controller/test_sensor.py b/tests/components/homekit_controller/test_sensor.py
index e17ad2a8c73..13d844e0162 100644
--- a/tests/components/homekit_controller/test_sensor.py
+++ b/tests/components/homekit_controller/test_sensor.py
@@ -4,6 +4,7 @@ from tests.components.homekit_controller.common import FakeService, setup_test_c
 TEMPERATURE = ("temperature", "temperature.current")
 HUMIDITY = ("humidity", "relative-humidity.current")
 LIGHT_LEVEL = ("light", "light-level.current")
+CARBON_DIOXIDE_LEVEL = ("carbon-dioxide", "carbon-dioxide.level")
 
 
 def create_temperature_sensor_service():
@@ -36,6 +37,16 @@ def create_light_level_sensor_service():
     return service
 
 
+def create_carbon_dioxide_level_sensor_service():
+    """Define carbon dioxide level characteristics."""
+    service = FakeService("public.hap.service.sensor.carbon-dioxide")
+
+    cur_state = service.add_characteristic("carbon-dioxide.level")
+    cur_state.value = 0
+
+    return service
+
+
 async def test_temperature_sensor_read_state(hass, utcnow):
     """Test reading the state of a HomeKit temperature sensor accessory."""
     sensor = create_temperature_sensor_service()
@@ -76,3 +87,17 @@ async def test_light_level_sensor_read_state(hass, utcnow):
     helper.characteristics[LIGHT_LEVEL].value = 20
     state = await helper.poll_and_get_state()
     assert state.state == "20"
+
+
+async def test_carbon_dioxide_level_sensor_read_state(hass, utcnow):
+    """Test reading the state of a HomeKit carbon dioxide sensor accessory."""
+    sensor = create_carbon_dioxide_level_sensor_service()
+    helper = await setup_test_component(hass, [sensor], suffix="co2")
+
+    helper.characteristics[CARBON_DIOXIDE_LEVEL].value = 10
+    state = await helper.poll_and_get_state()
+    assert state.state == "10"
+
+    helper.characteristics[CARBON_DIOXIDE_LEVEL].value = 20
+    state = await helper.poll_and_get_state()
+    assert state.state == "20"