Carbon monoxide detected

The Carbon monoxide detected condition passes when one or more carbon monoxide sensors are actively detecting carbon monoxide (CO). Because CO is colorless and odorless, your sensors are the only way to know it is there. Adding this condition to your automation ensures that safety actions, like sounding an alarm, turning on ventilation, or sending an urgent notification, only happen while the danger is confirmed. It prevents false alarms from a sensor that briefly flickered and keeps your response focused on real threats.

Using this condition from the user interface

If you prefer building automations visually, Home Assistant walks you through this condition step by step. You pick what to check, tweak a few options, and save. No YAML knowledge required.

To use this condition in an automation:

1. Go to Settings > Automations & scenes.
2. Open an existing automation, or select Create automation > Create new automation.
3. In the And if section, select Add condition.
4. Select what you want to check. Under By target (see Targets), pick the area your CO sensor is in (like your kitchen or garage). You can also select a floor, a device, a specific entity, or a label.
5. From the conditions shown for that target, select Carbon monoxide detected.
6. Under Condition passes if (see Behavior), pick Any or All to control how the check behaves when multiple sensors are targeted.
7. Select Save.

Options in the UI

Using this condition in YAML

If you work directly in YAML, or you want to know exactly what Home Assistant does under the hood, this section has the technical reference. It lists the field names you use in YAML, their types, and which ones are required. For how an automation is built in YAML, refer to Automations in YAML.

In YAML, put the settings that are specific to this condition under options. Keep target, if the condition uses one, and general settings such as alias and enabled at the top level, next to condition.

In YAML, refer to this condition as air_quality.is_co_detected. A basic example looks like this:

condition: air_quality.is_co_detected
target:
  entity_id: binary_sensor.hallway_co

This passes when the hallway carbon monoxide sensor is currently detecting CO.

Options in YAML

Targets of the condition

This condition requires a target. The target is the object that Home Assistant will check. You can point the condition at a single entityAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more], a device, an area, a floor, or a label, and Home Assistant will evaluate every matching carbon monoxide detector behind that target.

• Entity: one specific carbon monoxide detector, such as binary_sensor.hallway_carbon_monoxide.
• Device: every carbon monoxide detector that belongs to a device.
• Area: every carbon monoxide detector in a room or area.
• Floor: every carbon monoxide detector on a floor.
• Label: every carbon monoxide detector that shares a label.

You can also select different target types in one condition. For example, you can add a specific entity and an area as targets in the same condition to check both of them at once.

To learn which entities Home Assistant includes for a device, area, floor, or label, and how it handles several entities, refer to Automation targets.

Behavior with multiple targets

When you target more than one entity (or select an area, floor, or label that contains several), the Condition passes if option controls how the results combine:

• Any (default): the condition passes if at least one of the targeted entities matches. For example, if you check three smoke sensors and only one of them detects smoke, the condition still passes. This is useful for questions like “is there smoke anywhere in the house?”
• All: the condition passes only when every targeted entity matches. For example, if you check the same three smoke sensors, the condition passes only once all three report cleared. This is useful for “is the entire house safe now?” checks, so your automation does not send an all-clear while one room still has a reading.

Good to know

• Sensors that are unavailable or unknown are skipped. With Any, the condition passes if at least one of the other targeted sensors matches. With All, it passes if all the other targeted sensors match. If all targeted sensors are unavailable or unknown, All passes and Any fails.
• To check whether carbon monoxide is no longer detected, use Carbon monoxide cleared.
• To check the actual CO concentration rather than just a binary detection, use Carbon monoxide value.

Try it yourself

Ready to test this? Go to Settings > Automations & scenes, open an automation, and add this condition. Trigger the automation with and without the condition met, and watch whether it continues or stops.

More examples

Real scenarios where this condition gates an automation. Copy any example and adapt it to your setup. In the visual editor, select the UI options listed in the example or paste the YAML code.

Automation: warn the family when someone arrives home during a CO event

If carbon monoxide built up while the family was out, the first person home needs a warning before walking inside. This automation triggers when someone enters the home zone and checks whether the hallway CO sensor is still detecting carbon monoxide. If it is, an urgent notification tells them to stay outside and call emergency services.

• Trigger: Zone entered
  • Target: Frenck
  • Zone: Home
• Condition: Carbon monoxide detected
  • Target: Hallway CO sensor
  • Condition passes if: Any
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "CO warning on arrival home"
triggers:
  - trigger: zone.entered
    target:
      entity_id: person.frenck
    options:
      zone: zone.home
conditions:
  - condition: air_quality.is_co_detected
    target:
      entity_id: binary_sensor.hallway_co
    options:
      behavior: any
actions:
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      title: "Carbon monoxide detected at home"
      message: >
        The hallway CO sensor is detecting carbon
        monoxide. Stay outside and call emergency services.

Still stuck?

To find out why the condition didn’t pass, check it live in the automation editor, and look at the trace of the run. For details, refer to Testing automations. For common problems and their solutions, refer to Troubleshooting automations.

If that doesn’t help, the Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with the condition you’re using and what you expected to happen, or share on our subreddit /r/homeassistant.

Related conditions

Explore related conditions:

• Carbon monoxide cleared: Tests if one or more carbon monoxide sensors are cleared.

• Carbon monoxide value: Tests the carbon monoxide level of one or more entities.