PM1 value

The PM1 value condition passes when a PM1 sensor’s reading meets a specific level. PM1 refers to ultra-fine particulate matter smaller than 1 micrometer in diameter, particles so tiny they travel deep into the lungs. Cooking on a gas stove or burning a candle sends PM1 readings up quickly. This condition lets you start an air purifier only when ultra-fine particles are genuinely elevated, saving energy on quiet days and protecting your family when it matters.

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 this condition 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 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 conditions shown for that target, select PM1 value.
6. Under Threshold type, set the PM1 level the condition checks against.
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, refer to this condition as air_quality.is_pm1_value. A basic example looks like this:

condition: air_quality.is_pm1_value
target:
  entity_id: sensor.bedroom_pm1
options:
  threshold: 25
  behavior: any

This passes when the bedroom PM1 sensor reads at or above 25 µg/m³.

Options in YAML

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

Targets

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

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 (unavailable) or have an unknown state (unknown) are skipped for Any and fail for All.
• For coarser particulate readings, see
  • PM2.5 value
  • PM4 value
  • PM10 value

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.

Automation: start the bedroom purifier at bedtime only if PM1 is elevated

Ultra-fine particles from cooking, candles, or the heating system linger in a closed bedroom. This automation triggers at bedtime and checks the current PM1 reading. If the level is at or above 25 μg/m3, the air purifier turns on so you breathe clean air while you sleep. On evenings when the air is already fresh, the purifier stays off and the bedroom stays quiet.

• Trigger: Time: 22:00
• Condition: Air Quality: PM1 value
• Target: Bedroom PM1 sensor
• Threshold type: 25
• Condition passes if: Any
• Action: Fan: Turn on (air purifier)

alias: "Bedroom purifier at bedtime if PM1 is high"
triggers:
  - trigger: time
    at: "22:00:00"
conditions:
  - condition: air_quality.is_pm1_value
    target:
      entity_id: sensor.bedroom_pm1
    options:
      threshold: 25
      behavior: any
actions:
  - action: fan.turn_on
    target:
      entity_id: fan.bedroom_purifier

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

These conditions work well alongside this one:

• PM2.5 value - Tests the PM2.5 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.