Nitrous oxide value

The Nitrous oxide value condition passes when a nitrous oxide (N2O) sensor’s reading meets a specific level. N2O is a greenhouse gas that shows up in agricultural settings, greenhouses, and some industrial spaces. If you monitor a greenhouse or workshop, this condition lets your automation turn on ventilation only when N2O levels genuinely need attention, keeping fans off during normal readings so you save energy and reduce noise.

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 Nitrous oxide value.
6. Under Threshold type, set the N2O 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_n2o_value. A basic example looks like this:

condition: air_quality.is_n2o_value
target:
  entity_id: sensor.greenhouse_n2o
options:
  threshold: 500
  behavior: any

This passes when the greenhouse N2O sensor reads at or above 500 ppb.

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 related nitrogen-based pollutants, see Nitrogen monoxide value and Nitrogen dioxide 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.

Automation: ventilate the greenhouse each morning only if N2O is elevated

Fertilizer off-gassing raises N2O levels overnight in an enclosed greenhouse, especially on warm nights. This automation runs each morning at sunrise and checks the current reading. If N2O is at or above 500 ppb, the ventilation fan turns on so the air is fresh before you start working. On mornings when levels stayed low, the fan stays off, keeping the greenhouse warm and saving energy.

• Trigger: Sun: At sunrise
• Condition: Air Quality: Nitrous oxide value
• Target: Greenhouse N2O sensor
• Threshold type: 500
• Condition passes if: Any
• Action: Fan: Turn on

alias: "Morning greenhouse ventilation if N2O is high"
triggers:
  - trigger: sun
    event: sunrise
conditions:
  - condition: air_quality.is_n2o_value
    target:
      entity_id: sensor.greenhouse_n2o
    options:
      threshold: 500
      behavior: any
actions:
  - action: fan.turn_on
    target:
      entity_id: fan.greenhouse_ventilation

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:

• Nitrogen monoxide value - Tests the nitrogen monoxide level of one or more entities.

• Nitrogen dioxide value - Tests the nitrogen dioxide level of one or more entities.