Nitrous oxide level changed

The Nitrous oxide level changed trigger fires after the nitrous oxide (N2O) reading on one or more air quality sensors changes. Nitrous oxide is a potent greenhouse gas produced by agricultural activities, industrial processes, and combustion of fossil fuels. While it is less commonly monitored at home than other pollutants, specialized sensors track it in greenhouses, workshops near agricultural operations, and laboratory or medical settings.

Imagine your greenhouse ventilation fans spinning up automatically when N2O rises after a round of fertilizing, keeping the growing environment healthy without an extra trip outside. Use this trigger to log environmental data, activate ventilation, or send alerts when your N2O sensor reports a change. Use the threshold type to filter which changes matter to your automation.

Using this trigger from the user interface

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

To use Nitrous oxide level changed in an automation:

1. Go to Settings > Automations & scenes.
2. Open an existing automation, or select Create automation > Create new automation.
3. In the When section, select Add trigger.
4. Select what you want to monitor. 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. When you target multiple entities (via area, label, or multiple entity selections), the trigger fires whenever any of them changes.
5. From the triggers shown for that target, select Nitrous oxide level changed.
6. Under Threshold type, configure what kind of change fires the trigger:
   • Select Any change to fire on any change, regardless of direction or new value.
   • Select Above or Below and enter a value to fire only when the new reading is above or below that value.
   • Select In range and enter a lower and upper bound to fire only when the new reading falls inside the range.
   • Select Outside range and enter a lower and upper bound to fire only when the new reading is outside the range.
   • For each option, you can enter a fixed level in μg/m³, pick a sensor entity or a number helper entity as the threshold.
     • If you don’t have a number helper, you can create one by selecting Create a new number helper.
7. Select Save.

Options in the UI

Using this trigger 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 trigger under options. Keep target, if the trigger uses one, and general settings such as id, alias, enabled, and variables at the top level, next to trigger.

When this trigger starts an automation, it passes data about what happened to the automation. You can use this trigger data in the templates of your conditions and actions. To see which data is available, refer to Trigger data in templates.

In YAML, refer to this trigger as air_quality.n2o_changed. A basic example looks like this:

trigger: air_quality.n2o_changed
target:
  entity_id: sensor.greenhouse_n2o
options:
  threshold:
    type: above
    value:
      number: 900

This fires whenever the greenhouse N2O sensor reading changes to a value above 900 μg/m³. To fire on any change, use type: any and leave out value.

Options in YAML

Targets of the trigger

This trigger requires a target. The target is the object that Home Assistant will watch. You can select 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 as a target, and Home Assistant will watch 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 trigger. For example, you can add a specific entity and an area as targets in the same trigger to monitor 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.

Trigger variables

When the trigger reacts, the trigger variable identifies the entity that made it react. This is useful when a target contains multiple entities, such as a device, area, floor, or label.

The following trigger-specific variables are available:

• trigger.entity_id: Entity ID of the entity that made the trigger react.
• trigger.from_state: Previous state object of that entity.
• trigger.to_state: New state object of that entity.
• trigger.for: Timedelta object of how long the trigger criteria were met, if applicable.

For example, use {{ trigger.to_state.name }} in an action to include the name of the entity that made the trigger react in a notification.

The trigger variable describes the entity that made the trigger react. It doesn’t contain all the entities of the target.

Good to know

• Nitrous oxide is a potent greenhouse gas with roughly 300 times the warming potential of carbon dioxide. Monitoring it is valuable for environmental tracking.
• The threshold type controls which changes fire the trigger. Use Above or Below to fire only when the new level is above or below a value, In range to fire only when it’s inside a range, and Outside range to fire only when it’s outside a range. Use Any change to fire on every change.
• To react only when N2O crosses a specific concentration in one direction, use Nitrous oxide level crossed threshold instead.
• 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, create a new automation, and add this trigger. Save the automation, and then make the trigger react. For example, change the state of the targeted 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], turn on a light that the trigger monitors, or change its brightness. To check whether the automation ran, open its traces.

More examples

Real scenarios where this trigger fires in automations and scripts. Copy any example and adapt it to your setup. In the visual editor, select the UI options listed in the example when they are available, or paste the YAML code.

Automation: ventilate the greenhouse on N2O change

After fertilizing, N2O levels in a greenhouse tend to climb. This automation turns on the ventilation fans when N2O levels change to a value above 900 μg/m³, keeping the growing environment healthy for your plants without an extra trip outside to check.

• Trigger: Nitrous oxide level changed
  • Target: Greenhouse N2O sensor
  • Threshold type: Above 900 μg/m³
• Action: Turn on fan

alias: "Ventilate greenhouse on N2O change"
triggers:
  - trigger: air_quality.n2o_changed
    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 trigger you’re using and what you expected to happen, or share on our subreddit /r/homeassistant.

Related triggers

Explore related triggers:

• Nitrous oxide level crossed threshold: Triggers when one or more nitrous oxide levels cross a threshold.