PM2.5 value

The PM2.5 value condition passes when a PM2.5 sensor’s reading meets a specific level. PM2.5 is the most widely used indicator of air quality, and for good reason: these fine particles (smaller than 2.5 micrometers) come from traffic, wildfires, and everyday cooking, and they affect respiratory health at surprisingly low concentrations. This condition gives your automation precision, closing the windows only when outdoor PM2.5 is above a safe limit or holding off on opening them until the reading drops back down.

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 PM2.5 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 PM2.5 sensor is in (like your living room or bedroom). You can also select a device, a specific entity, or a label.
5. From the conditions shown for that target, select PM2.5 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 35 for 35 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. 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_pm25_value. A basic example looks like this:

condition: air_quality.is_pm25_value
target:
  entity_id: sensor.living_room_pm25
options:
  threshold:
    type: above
    value:
      number: 35
  behavior: any

This passes when the living room PM2.5 sensor reads above 35 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 PM2.5 sensor behind that target.

• Entity: one specific PM2.5 sensor, such as sensor.living_room_pm25.
• Device: every PM2.5 sensor that belongs to a device.
• Area: every PM2.5 sensor in a room or area.
• Floor: every PM2.5 sensor on a floor.
• Label: every PM2.5 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.
• The World Health Organization recommends keeping 24-hour average PM2.5 exposure below 15 μg/m³.
• For other particle sizes, see
  • PM1 value
  • PM4 value
  • PM10 value
• The threshold is in μg/m³. A sensor that reports PM2.5 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: check outdoor PM2.5 before opening the windows each morning

During wildfire season, outdoor PM2.5 readings spike overnight while you sleep. This automation triggers when you open the living room window cover and checks the outdoor PM2.5 reading first. If the level is above 35 μg/m³, the cover closes right back and you get a notification letting you know the air outside is not safe for ventilation. On clear mornings, nothing happens and you enjoy the fresh air.

• Trigger: State changed: Living room window cover opened
• Condition: PM2.5 value
  • Target: Outdoor PM2.5 sensor
  • Threshold type: Above 35 μg/m³
  • Condition passes if: Any
• Action: Close cover
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "Close windows if outdoor PM2.5 is high"
triggers:
  - trigger: state
    entity_id: cover.living_room_window
    to: open
conditions:
  - condition: air_quality.is_pm25_value
    target:
      entity_id: sensor.outdoor_pm25
    options:
      threshold:
        type: above
        value:
          number: 35
      behavior: any
actions:
  - action: cover.close_cover
    target:
      entity_id: cover.living_room_window
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      title: "PM2.5 is high outside"
      message: >
        Outdoor PM2.5 is above 35 μg/m³. The window
        has been closed to keep the air clean.

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:

• PM1 value: Tests the PM1 level of one or more entities.

• PM4 value: Tests the PM4 level of one or more entities.

• PM10 value: Tests the PM10 level of one or more entities.