PM1 level changed

The PM1 level changed trigger fires after the PM1 (particulate matter 1 micrometer or smaller) reading on one or more air quality sensors changes by a meaningful amount. PM1 particles are ultrafine and originate from combustion, vehicle exhaust, and industrial emissions. Because of their tiny size, they penetrate deep into the lungs and bloodstream. Cooking on a gas stove, nearby traffic, or a wildfire miles away all push PM1 levels up inside your home.

Imagine your nursery air purifier ramping up the moment particle levels shift, keeping the air as clean as possible for little ones without you doing antything. Use this trigger to start an air purifier, adjust HVAC filtration, or log particle count changes when your PM1 sensor reports a significant shift.

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 this trigger 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 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 triggers shown for that target, select PM1 level changed.
6. Under Threshold type, set how much the level has to change before the trigger fires.
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, refer to this trigger as air_quality.pm1_changed. A basic example looks like this:

trigger: air_quality.pm1_changed
target:
  entity_id: sensor.living_room_pm1
options:
  threshold: 5

This fires whenever the living room PM1 sensor reading changes by at least 5 micrograms per cubic meter.

Options in YAML

YAML sometimes provides additional options for more complex use cases that are not available through the UI.

Targets

This trigger supports targets. A target tells Home Assistant what the trigger should watch. 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 watches 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 trigger. For example, combine a specific entity with an area to watch both at once.

Good to know

• PM1 particles are the smallest commonly measured particulate matter. They are especially relevant for respiratory health.
• The trigger fires on any change that meets the threshold, whether the level goes up or down.
• To react only when PM1 crosses a specific concentration in one direction, use PM1 level crossed threshold instead.

Try it yourself

Ready to test this? Go to Settings > Automations & scenes, create a new automation, and add this trigger. Save the automation, then change the state of the targeted entity to watch the trigger fire on your actual entitiesAn 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].

More examples

Real scenarios where this trigger fires in automations and scripts. Copy any example and adapt it to your setup.

Automation: boost the air purifier when PM1 shifts

Ultrafine particles from cooking or traffic drift into every room, and tiny lungs are the most vulnerable. This automation increases your air purifier speed whenever PM1 levels in the nursery shift noticeably, keeping the air as clean as possible for little ones.

• Trigger: PM1 level changed
• Target: Nursery PM1 sensor
• Threshold type: 5
• Action: Fan: Set speed

alias: "Boost purifier on PM1 change"
triggers:
  - trigger: air_quality.pm1_changed
    target:
      entity_id: sensor.nursery_pm1
    options:
      threshold: 5
actions:
  - action: fan.set_percentage
    target:
      entity_id: fan.nursery_air_purifier
    data:
      percentage: 80

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

These triggers work well alongside this one:

• PM1 level crossed threshold - Triggers after one or more PM1 levels cross a threshold.