PM4 value

The PM4 value condition passes when a PM4 sensor’s reading meets a specific level. PM4 covers particulate matter smaller than 4 micrometers in diameter, a size range that bridges fine and coarse particles. Some sensors report PM4 alongside PM2.5 and PM10, giving you a more complete picture of what is floating in the air. This condition lets your automation react when PM4 readings are elevated, for example sending a notification that your air filter is due for a check.

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 PM4 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 PM4 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 PM4 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 50 for 50 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_pm4_value. A basic example looks like this:

condition: air_quality.is_pm4_value
target:
  entity_id: sensor.living_room_pm4
options:
  threshold:
    type: above
    value:
      number: 50
  behavior: any

This passes when the living room PM4 sensor reads above 50 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 PM4 sensor behind that target.

• Entity: one specific PM4 sensor, such as sensor.living_room_pm4.
• Device: every PM4 sensor that belongs to a device.
• Area: every PM4 sensor in a room or area.
• Floor: every PM4 sensor on a floor.
• Label: every PM4 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 other particle sizes, see
  • PM1 value
  • PM2.5 value
  • PM10 value
• The threshold is in μg/m³. A sensor that reports PM4 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: send a weekly filter reminder only if PM4 is elevated

If your indoor PM4 readings are consistently high, the air filters are likely overdue for a swap. This automation runs every Sunday morning and checks the living room PM4 reading. If the level is above 50 μg/m³, you get a reminder to check the filters. On weeks when the air is clean, no notification is sent.

• Trigger: Time: Every Sunday at 09:00
• Condition: PM4 value
  • Target: Living room PM4 sensor
  • Threshold type: Above 50 μg/m³
  • Condition passes if: Any
• Action: Send a notification message
  • Target: My Device (notify.my_device)

alias: "Weekly filter reminder if PM4 is high"
triggers:
  - trigger: time
    at: "09:00:00"
conditions:
  - condition: time
    weekday:
      - sun
  - condition: air_quality.is_pm4_value
    target:
      entity_id: sensor.living_room_pm4
    options:
      threshold:
        type: above
        value:
          number: 50
      behavior: any
actions:
  - action: notify.send_message
    target:
      entity_id: notify.my_device
    data:
      title: "Time to check the air filters"
      message: >
        The living room PM4 reading is above 50 μg/m³.
        Your air filters might need replacing.

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:

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

• PM2.5 value: Tests the PM2.5 level of one or more entities.

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