[aqi] Add NowCast AQI sensor using PM2.5 and PM10

[bharvey88]

Version: 25.12.18.2

What does this implement/fix?

Adds a NowCast AQI sensor to the AIR-1 using the built-in ESPHome aqi platform. The sensor takes PM2.5 and PM10 readings from the SEN55, computes an AQI sub-index for each using 2024 EPA breakpoints, and publishes the worse of the two values. The entity exposes device_class: aqi so Home Assistant formats and colours it correctly.

Why "NowCast AQI" and not "AQI"?

A true US EPA Air Quality Index requires ozone (O₃) and sulfur dioxide (SO₂) sub-indices that the AIR-1 hardware does not measure. This value is computed from PM2.5 and PM10 only using the 2024 EPA breakpoints and should be understood as a particulate-matter air quality indicator, not a certified AQI reading.

Reference: EPA Technical Assistance Document for the Reporting of Daily Air Quality

The sensor is callback-driven — it updates the moment either PM sensor publishes a new reading, so no additional poll interval is needed and it adds no overhead to the reportAllValues script.

Types of changes

• Bugfix (fixed change that fixes an issue)
• New feature (thanks!)
• Breaking change (repair/feature that breaks existing functionality)
• Dependency Update - Does not publish
• Other - Does not publish
• Website of github readme file update - Does not publish
• Github workflows - Does not publish

Checklist / Checklijst:

• The code change has been tested and works locally
• The code change has not yet been tested

If user-visible functionality or configuration variables are added/modified:

• Added/updated documentation for the web page

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📥 Commits

Reviewing files that changed from the base of the PR and between aa6e149 and 797ee73.

📒 Files selected for processing (1)

• Integrations/ESPHome/Core.yaml

Walkthrough

A new AQI (Air Quality Index) sensor configuration was added to the ESPHome Core.yaml file. The sensor platform monitors air quality using PM2.5 and PM10.0 particle measurements, applying the NowCast AQI calculation method.

Changes

Cohort / File(s)	Summary
ESPHome AQI Sensor Configuration Integrations/ESPHome/Core.yaml	Added new AQI sensor platform entry with id nowcast_aqi that calculates NowCast AQI from existing PM2.5 and PM10.0 sensor readings.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A whisker-twitched addition to the air,
NowCast AQI, floating there,
PM particles dance and swirl,
A sensor's gentle quality-whirl! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: adding a NowCast AQI sensor that uses PM2.5 and PM10 measurements, which aligns perfectly with the file modification in Core.yaml.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch aqi-nowcast-sensor

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@Integrations/ESPHome/Core.yaml`:
- Around line 310-315: The AQI sensor block using platform: aqi (id:
nowcast_aqi, calculation_type: AQI) does not set a device_class, so add an
explicit device_class: aqi entry to that sensor definition to ensure Home
Assistant recognizes it correctly (i.e., update the sensor with id nowcast_aqi
to include device_class: aqi).

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ℹ️ Review info

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between e523911 and aa6e149.

📒 Files selected for processing (1)

• Integrations/ESPHome/Core.yaml