diff --git a/docs/core/entity/binary-sensor.md b/docs/core/entity/binary-sensor.md
index bb86769c..4c0f5706 100644
--- a/docs/core/entity/binary-sensor.md
+++ b/docs/core/entity/binary-sensor.md
@@ -22,6 +22,7 @@ Properties should always only return information from memory and not do I/O (lik
 | ----- | -----------
 | battery | On means low, Off means normal.
 | battery_charging | On means charging, Off means not charging.
+| co | On means carbon monoxide detected, Off means no carbon monoxide (clear).
 | cold | On means cold, Off means normal.
 | connectivity | On means connected, Off means disconnected.
 | door | On means open, Off means closed.