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 PM1 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 PM1 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 PM1 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 25 for 25 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_pm1_value. A basic example looks like this:

condition: air_quality.is_pm1_value
target:
  entity_id: sensor.bedroom_pm1
options:
  threshold:
    type: above
    value:
      number: 25
  behavior: any

This passes when the bedroom PM1 sensor reads above 25 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 PM1 sensor behind that target.

• Entity: one specific PM1 sensor, such as sensor.living_room_pm1.
• Device: every PM1 sensor that belongs to a device.
• Area: every PM1 sensor in a room or area.
• Floor: every PM1 sensor on a floor.
• Label: every PM1 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 coarser particulate readings, see
  • PM2.5 value
  • PM4 value
  • PM10 value
• The threshold is in μg/m³. A sensor that reports PM1 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: 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 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: PM1 value
  • Target: Bedroom PM1 sensor
  • Threshold type: Above 25 μg/m³
• Action: Turn on fan
  • Target: Bedroom 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:
        type: above
        value:
          number: 25
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

Explore related conditions:

• 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.