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 Nitrous oxide value 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 nitrous oxide sensor is in (like your greenhouse or workshop). You can also select 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 level the condition checks against:
   1. Pick whether the reading must be Above, Below, In range, or Outside range of the threshold.
   2. Select Number or Entity:
      • Number: Enter a fixed level directly, for example 900 for 900 μg/m³. For In range or Outside range, enter both a lower and upper bound.
      • Entity: Use a sensor entity or a number helper entity as the threshold:
        • Number helper: You can adjust the threshold value without editing the automation. The sensor reading is compared against the number helper’s current value.
        • Sensor: Its current reading becomes the threshold and updates automatically as the sensor changes.
        • For In range or Outside range, you need two entities: one for the lower bound and one for the upper bound (for example, two separate number helpers).
        • If you don’t have a number helper, you can create one by selecting Create a new number helper.
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, 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_n2o_value. A basic example looks like this:

condition: air_quality.is_n2o_value
target:
  entity_id: sensor.greenhouse_n2o
options:
  threshold:
    type: above
    value:
      number: 900
  behavior: any

This passes when the greenhouse N2O sensor reads above 900 μg/m³.

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 nitrous oxide sensor behind that target.

• Entity: one specific nitrous oxide sensor, such as sensor.living_room_nitrous_oxide.
• Device: every nitrous oxide sensor that belongs to a device.
• Area: every nitrous oxide sensor in a room or area.
• Floor: every nitrous oxide sensor on a floor.
• Label: every nitrous oxide sensor 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.
• For related nitrogen-based pollutants, see Nitrogen monoxide value and Nitrogen dioxide value.
• The threshold is in μg/m³. A sensor that reports N2O in another unit never matches. If you use an entity as the threshold, it must also report μg/m³.

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: 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 above 900 μg/m³, 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: Sunrise
• Condition: Nitrous oxide value
  • Target: Greenhouse N2O sensor
  • Threshold type: Above 900 μg/m³
• Action: Turn on fan
  • Target: Greenhouse ventilation

alias: "Morning greenhouse ventilation if N2O is high"
triggers:
  - trigger: sun.sunrise
conditions:
  - condition: air_quality.is_n2o_value
    target:
      entity_id: sensor.greenhouse_n2o
    options:
      threshold:
        type: above
        value:
          number: 900
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

Explore related conditions:

• 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.