diff --git a/homeassistant/components/ambient_station/__init__.py b/homeassistant/components/ambient_station/__init__.py
index b4ac6992459..bee5ab33db7 100644
--- a/homeassistant/components/ambient_station/__init__.py
+++ b/homeassistant/components/ambient_station/__init__.py
@@ -18,6 +18,7 @@ from homeassistant.const import (
     CONCENTRATION_PARTS_PER_MILLION,
     CONF_API_KEY,
     DEGREE,
+    DEVICE_CLASS_CO2,
     EVENT_HOMEASSISTANT_STOP,
     IRRADIATION_WATTS_PER_SQUARE_METER,
     LIGHT_LUX,
@@ -159,7 +160,7 @@ SENSOR_TYPES = {
     TYPE_BATT8: ("Battery 8", None, BINARY_SENSOR, "battery"),
     TYPE_BATT9: ("Battery 9", None, BINARY_SENSOR, "battery"),
     TYPE_BATTOUT: ("Battery", None, BINARY_SENSOR, "battery"),
-    TYPE_CO2: ("co2", CONCENTRATION_PARTS_PER_MILLION, SENSOR, None),
+    TYPE_CO2: ("co2", CONCENTRATION_PARTS_PER_MILLION, SENSOR, DEVICE_CLASS_CO2),
     TYPE_DAILYRAININ: ("Daily Rain", "in", SENSOR, None),
     TYPE_DEWPOINT: ("Dew Point", TEMP_FAHRENHEIT, SENSOR, "temperature"),
     TYPE_EVENTRAININ: ("Event Rain", "in", SENSOR, None),
diff --git a/homeassistant/components/awair/const.py b/homeassistant/components/awair/const.py
index 44490b8401f..2853ef9dd6c 100644
--- a/homeassistant/components/awair/const.py
+++ b/homeassistant/components/awair/const.py
@@ -12,6 +12,7 @@ from homeassistant.const import (
     CONCENTRATION_MICROGRAMS_PER_CUBIC_METER,
     CONCENTRATION_PARTS_PER_BILLION,
     CONCENTRATION_PARTS_PER_MILLION,
+    DEVICE_CLASS_CO2,
     DEVICE_CLASS_HUMIDITY,
     DEVICE_CLASS_ILLUMINANCE,
     DEVICE_CLASS_TEMPERATURE,
@@ -104,7 +105,7 @@ SENSOR_TYPES = {
         ATTR_UNIQUE_ID: "PM10",  # matches legacy format
     },
     API_CO2: {
-        ATTR_DEVICE_CLASS: None,
+        ATTR_DEVICE_CLASS: DEVICE_CLASS_CO2,
         ATTR_ICON: "mdi:cloud",
         ATTR_UNIT: CONCENTRATION_PARTS_PER_MILLION,
         ATTR_LABEL: "Carbon dioxide",
diff --git a/homeassistant/components/fibaro/sensor.py b/homeassistant/components/fibaro/sensor.py
index 4e9af8803f2..40a843bc7bb 100644
--- a/homeassistant/components/fibaro/sensor.py
+++ b/homeassistant/components/fibaro/sensor.py
@@ -2,6 +2,7 @@
 from homeassistant.components.sensor import DOMAIN
 from homeassistant.const import (
     CONCENTRATION_PARTS_PER_MILLION,
+    DEVICE_CLASS_CO2,
     DEVICE_CLASS_HUMIDITY,
     DEVICE_CLASS_ILLUMINANCE,
     DEVICE_CLASS_TEMPERATURE,
@@ -27,7 +28,13 @@ SENSOR_TYPES = {
         "mdi:fire",
         None,
     ],
-    "CO2": ["CO2", CONCENTRATION_PARTS_PER_MILLION, "mdi:cloud", None],
+    "CO2": [
+        "CO2",
+        CONCENTRATION_PARTS_PER_MILLION,
+        None,
+        None,
+        DEVICE_CLASS_CO2,
+    ],
     "com.fibaro.humiditySensor": [
         "Humidity",
         PERCENTAGE,
diff --git a/homeassistant/components/netatmo/sensor.py b/homeassistant/components/netatmo/sensor.py
index 9176b670bea..efda94d6399 100644
--- a/homeassistant/components/netatmo/sensor.py
+++ b/homeassistant/components/netatmo/sensor.py
@@ -8,6 +8,7 @@ from homeassistant.const import (
     CONCENTRATION_PARTS_PER_MILLION,
     DEGREE,
     DEVICE_CLASS_BATTERY,
+    DEVICE_CLASS_CO2,
     DEVICE_CLASS_HUMIDITY,
     DEVICE_CLASS_PRESSURE,
     DEVICE_CLASS_SIGNAL_STRENGTH,
@@ -52,7 +53,7 @@ SUPPORTED_PUBLIC_SENSOR_TYPES = [
 SENSOR_TYPES = {
     "temperature": ["Temperature", TEMP_CELSIUS, None, DEVICE_CLASS_TEMPERATURE, True],
     "temp_trend": ["Temperature trend", None, "mdi:trending-up", None, False],
-    "co2": ["CO2", CONCENTRATION_PARTS_PER_MILLION, "mdi:molecule-co2", None, True],
+    "co2": ["CO2", CONCENTRATION_PARTS_PER_MILLION, None, DEVICE_CLASS_CO2, True],
     "pressure": ["Pressure", PRESSURE_MBAR, None, DEVICE_CLASS_PRESSURE, True],
     "pressure_trend": ["Pressure trend", None, "mdi:trending-up", None, False],
     "noise": ["Noise", "dB", "mdi:volume-high", None, True],
diff --git a/homeassistant/components/tasmota/sensor.py b/homeassistant/components/tasmota/sensor.py
index 39577e9e558..0387e835522 100644
--- a/homeassistant/components/tasmota/sensor.py
+++ b/homeassistant/components/tasmota/sensor.py
@@ -9,6 +9,7 @@ from homeassistant.const import (
     CONCENTRATION_PARTS_PER_BILLION,
     CONCENTRATION_PARTS_PER_MILLION,
     DEVICE_CLASS_BATTERY,
+    DEVICE_CLASS_CO2,
     DEVICE_CLASS_HUMIDITY,
     DEVICE_CLASS_ILLUMINANCE,
     DEVICE_CLASS_POWER,
@@ -52,7 +53,7 @@ SENSOR_DEVICE_CLASS_ICON_MAP = {
     hc.SENSOR_APPARENT_POWERUSAGE: {DEVICE_CLASS: DEVICE_CLASS_POWER},
     hc.SENSOR_BATTERY: {DEVICE_CLASS: DEVICE_CLASS_BATTERY},
     hc.SENSOR_CCT: {ICON: "mdi:temperature-kelvin"},
-    hc.SENSOR_CO2: {ICON: "mdi:molecule-co2"},
+    hc.SENSOR_CO2: {DEVICE_CLASS: DEVICE_CLASS_CO2},
     hc.SENSOR_COLOR_BLUE: {ICON: "mdi:palette"},
     hc.SENSOR_COLOR_GREEN: {ICON: "mdi:palette"},
     hc.SENSOR_COLOR_RED: {ICON: "mdi:palette"},
diff --git a/tests/components/tasmota/test_sensor.py b/tests/components/tasmota/test_sensor.py
index c08b1b531de..2b7c388ca2f 100644
--- a/tests/components/tasmota/test_sensor.py
+++ b/tests/components/tasmota/test_sensor.py
@@ -446,9 +446,9 @@ async def test_attributes(hass, mqtt_mock, setup_tasmota):
     assert state.attributes.get("unit_of_measurement") == "°C"
 
     state = hass.states.get("sensor.tasmota_beer_CarbonDioxide")
-    assert state.attributes.get("device_class") is None
+    assert state.attributes.get("device_class") == "carbon_dioxide"
     assert state.attributes.get("friendly_name") == "Tasmota Beer CarbonDioxide"
-    assert state.attributes.get("icon") == "mdi:molecule-co2"
+    assert state.attributes.get("icon") is None
     assert state.attributes.get("unit_of_measurement") == "ppm"
 
 
@@ -516,9 +516,9 @@ async def test_indexed_sensor_attributes(hass, mqtt_mock, setup_tasmota):
     assert state.attributes.get("unit_of_measurement") == "°C"
 
     state = hass.states.get("sensor.tasmota_dummy2_carbondioxide_1")
-    assert state.attributes.get("device_class") is None
+    assert state.attributes.get("device_class") == "carbon_dioxide"
     assert state.attributes.get("friendly_name") == "Tasmota Dummy2 CarbonDioxide 1"
-    assert state.attributes.get("icon") == "mdi:molecule-co2"
+    assert state.attributes.get("icon") is None
     assert state.attributes.get("unit_of_measurement") == "ppm"