diff --git a/homeassistant/components/sensor/const.py b/homeassistant/components/sensor/const.py
index 8ab90f03c01..17155912e48 100644
--- a/homeassistant/components/sensor/const.py
+++ b/homeassistant/components/sensor/const.py
@@ -466,6 +466,7 @@ UNIT_CONVERTERS: dict[SensorDeviceClass | str | None, type[BaseUnitConverter]] =
     SensorDeviceClass.PRESSURE: PressureConverter,
     SensorDeviceClass.SPEED: SpeedConverter,
     SensorDeviceClass.TEMPERATURE: TemperatureConverter,
+    SensorDeviceClass.VOLATILE_ORGANIC_COMPOUNDS_PARTS: UnitlessRatioConverter,
     SensorDeviceClass.VOLTAGE: ElectricPotentialConverter,
     SensorDeviceClass.VOLUME: VolumeConverter,
     SensorDeviceClass.VOLUME_STORAGE: VolumeConverter,
diff --git a/homeassistant/util/unit_conversion.py b/homeassistant/util/unit_conversion.py
index 0fde15acd71..a22a204e69a 100644
--- a/homeassistant/util/unit_conversion.py
+++ b/homeassistant/util/unit_conversion.py
@@ -2,6 +2,8 @@
 from __future__ import annotations
 
 from homeassistant.const import (
+    CONCENTRATION_PARTS_PER_BILLION,
+    CONCENTRATION_PARTS_PER_MILLION,
     PERCENTAGE,
     UNIT_NOT_RECOGNIZED_TEMPLATE,
     UnitOfDataRate,
@@ -421,6 +423,8 @@ class UnitlessRatioConverter(BaseUnitConverter):
     NORMALIZED_UNIT = None
     _UNIT_CONVERSION: dict[str | None, float] = {
         None: 1,
+        CONCENTRATION_PARTS_PER_BILLION: 1000000000,
+        CONCENTRATION_PARTS_PER_MILLION: 1000000,
         PERCENTAGE: 100,
     }
     VALID_UNITS = {
diff --git a/tests/util/test_unit_conversion.py b/tests/util/test_unit_conversion.py
index 51b126bce3b..1aea64201b5 100644
--- a/tests/util/test_unit_conversion.py
+++ b/tests/util/test_unit_conversion.py
@@ -6,6 +6,8 @@ import inspect
 import pytest
 
 from homeassistant.const import (
+    CONCENTRATION_PARTS_PER_BILLION,
+    CONCENTRATION_PARTS_PER_MILLION,
     PERCENTAGE,
     UnitOfDataRate,
     UnitOfElectricCurrent,
@@ -365,6 +367,8 @@ _CONVERTED_VALUE: dict[
     ],
     UnitlessRatioConverter: [
         (5, None, 500, PERCENTAGE),
+        (5, None, 5000000000, CONCENTRATION_PARTS_PER_BILLION),
+        (5, None, 5000000, CONCENTRATION_PARTS_PER_MILLION),
         (5, PERCENTAGE, 0.05, None),
     ],
     VolumeConverter: [