Carbon monoxide value

The Carbon monoxide value condition passes when a carbon monoxide (CO) sensor’s reading meets a specific level. Carbon monoxide is a colorless, odorless gas produced by incomplete combustion, and even moderate levels deserve attention. This condition gives you finer control than simpler detected or cleared checks, letting you start ventilation at a lower reading and sound the full alarm only when concentrations climb higher.

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 air quality sensor is in (like your living room or bedroom). 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 value.
6. Under Threshold type, set the CO level the condition checks against.
7. Under Condition passes if (see Behavior), pick Any or All.
8. 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.

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

condition: air_quality.is_co_value
target:
  entity_id: sensor.hallway_co
options:
  threshold: 35
  behavior: any

This passes when the hallway CO sensor reads at or above 35 ppm.

Options in YAML

YAML sometimes provides additional options for more complex use cases that are not available through the UI.

Targets

This condition supports targets. A target tells Home Assistant what the condition should check. You can point it 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 evaluates every matching air_quality entity behind that target.

• Entity: one specific air_quality entity, such as air_quality.living_room.
• Device: every air_quality entity that belongs to a device.
• Area: every air_quality entity in a room or area.
• Floor: every air_quality entity on a floor.
• Label: every air_quality entity that shares a label.

You can also mix target types in one condition. For example, combine a specific entity with an area to check both at once.

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 (unavailable) or have an unknown state (unknown) are skipped for Any and fail for All.
• For simple binary detection without a specific threshold, use Carbon monoxide detected or Carbon monoxide cleared.

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.

Automation: check CO levels when you arrive home

When you pull into the driveway, you want to know if the air inside is safe before settling in. This automation triggers when you enter the home zone and checks the hallway CO reading. If the level is at or above 20 ppm, you get a notification right away so you know to open the windows or stay outside until the air clears.

• Trigger: Zone: Person enters home zone
• Condition: Air Quality: Carbon monoxide value
• Target: Hallway CO sensor
• Threshold type: 20
• Condition passes if: Any
• Action: Notify: Send notification

alias: "CO check on arrival home"
triggers:
  - trigger: zone
    entity_id: person.frenck
    zone: zone.home
    event: enter
conditions:
  - condition: air_quality.is_co_value
    target:
      entity_id: sensor.hallway_co
    options:
      threshold: 20
      behavior: any
actions:
  - action: notify.mobile_app_phone
    data:
      title: "CO level elevated at home"
      message: >
        The hallway CO reading is above 20 ppm.
        Open the windows before settling in.

Still stuck?

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

These conditions work well alongside this one:

• Carbon monoxide detected - Tests if one or more carbon monoxide sensors are detecting carbon monoxide.

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