Feature request: Generic AQI Component

[danielkent-net]

Describe the component you'd like

I would like a derived sensor type that can take raw sensor readings from attached sensors (or offboard) and convert them to a computed current air quality index (AQI) reading.

What are your use cases for this component?

Between all the sensors that are currently supported by ESPHome, it is feasible to calculate AQI (at least based on US or similar standards):

PM2.5, PM10: SEN5x (and SEN6X assuming support is merged soon)
NO2, CO: MiCS 4514
Ozone: SEN0321
Sulfur Dioxide: Unknown

A generic AQI component would allow users to create their own fully functional air quality measurement devices that can be compared against official readings.

Is there a public datasheet, documentation and/or schematics?

General information: https://en.wikipedia.org/wiki/Air_quality_index

US AQI standards: https://document.airnow.gov/technical-assistance-document-for-the-reporting-of-daily-air-quailty.pdf

Anything else?

Hypothetical configuration:

esphome:

...

sensor:
  # Example data sources for ingestion into aqi component
  - platform: sen5x
    id: sen5x_01
    model: sen55
    pm_2_5:
      name: sen55_01_pm_2_5
      ...
 - platform: mics_4514
   id: mics_4514_01
   nitrogen_dioxide:
     name: mics_01_no2
     ...
   carbon_monoxide:
    name: mics_01_co
    ...
 #  Actual proposed AQI component
 - platform: aqi
   name: "AQI"
   type: us
   data_timeout: 1hr
   instantaneous_measurements:
     name: "AQI (Instantaneous Measurements)"
   data_timeout_behavior: "bestguess"
  #data_timeout_behavior: "unavailable"
   components:
     - pm_2_5:
         source: sen55_01_pm_2_5
         avg_0h:
           name: "AQI (PM2.5)"
           publish: True
         avg_1h:
           name: "AQI (PM2.5) 1 hour Average"
           publish: False
         avg_8h:
           name: "AQI (PM2.5) 8 hour Average"
           publish: False
         avg_24h:
           name: "AQI (PM2.5) 24 hour Average"
           publish: True
     - pm_10_0: sen55_01_pm_10_0
     - co: mics_01_co
     - no2: mics_01_no2

I would be willing to put in some work on this idea. I am currently working on a header file to implement AQI calculations on device, which would form the basis for an eventual PR.

Current anticipated challenges:

• How to handle AQI when one or more sensor readings aren't present (proposed solution: compute AQI without considering those components, which I think is how cheaper sensors operate)
• Following the standards when time delays/averages are required. The US standard incorporates 24-hour averages for particulate, 8 hours for CO, and 1 hour for the other pollutants. Users may expect AQI to be available immediately. I could make it configurable to
• Similarly, users may want to know each AQI component - for example, the AQI measurement when considering PM2.5 alone, instead of in aggregate with other components. I intend to code this such that these readings can be either kept hidden, or published and available in Home Assistant.
• Implementing multiple AQI standards. I am in the US and am most interested in the US standard, but I will attempt to write my code in a reasonable way to allow extension to other AQI standards. The CN standard is based on the US standard, which should make implementation fairly straightforward. Some standards could be implemented with lookup tables (UK).