calculate-aqi

name	calculate-aqi
description	Use when a user has raw pollutant measurements and needs to convert them to AQI, or wants to understand how a specific reading maps to health impacts.

Calculate AQI from Pollutant Concentrations

Compute US EPA Air Quality Index (AQI) from raw pollutant readings. Supports PM2.5, PM10, O3, NO2, SO2, and CO.

When to use

• User has a pollutant reading and wants to know the AQI equivalence
• User needs to convert sensor data to standardized health categories
• User wants to compare concentrations across different scales or regions
• User needs to compute per-pollutant sub-AQI and identify the dominant pollutant

Inputs to gather

Any one or more of the following (supply units and averaging period):

• PM2.5: µg/m³, 24-hour average
• PM10: µg/m³, 24-hour average
• O3: ppb, 8-hour or 1-hour average (specify which)
• NO2: ppb, 1-hour average
• SO2: ppb, 1-hour average
• CO: ppm, 8-hour average

Procedure

1. For each pollutant provided, look up the AQI breakpoint table and compute sub-AQI.
2. EPA Breakpoints and Index Scale:
   • PM2.5 (µg/m³, 24h avg):
     • 0–12 → 0–50 | 12.1–35.4 → 51–100 | 35.5–55.4 → 101–150 | 55.5–150.4 → 151–200 | 150.5–250.4 → 201–300 | 250.5–500.4 → 301–500
   • PM10 (µg/m³, 24h avg):
     • 0–54 → 0–50 | 55–154 → 51–100 | 155–254 → 101–150 | 255–354 → 151–200 | 355–424 → 201–300 | 425–604 → 301–500
   • O3 (ppb, 8h avg):
     • 0–54 → 0–50 | 55–70 → 51–100 | 71–85 → 101–150 | 86–105 → 151–200 | 106–200 → 201–300 | >200 → 301–500
   • NO2 (ppb, 1h):
     • 0–53 → 0–50 | 54–100 → 51–100 | 101–360 → 101–150 | 361–649 → 151–200 | 650–1249 → 201–300 | >1249 → 301–500
   • SO2 (ppb, 1h):
     • 0–35 → 0–50 | 36–75 → 51–100 | 76–185 → 101–150 | 186–304 → 151–200 | 305–604 → 201–300 | >604 → 301–500
   • CO (ppm, 8h):
     • 0–4.4 → 0–50 | 4.5–9.4 → 51–100 | 9.5–12.4 → 101–150 | 12.5–15.4 → 151–200 | 15.5–30.4 → 201–300 | 30.5–50.4 → 301–500
3. For each pollutant, use linear interpolation within the applicable breakpoint band:

   AQI = ((I_hi - I_lo) / (BP_hi - BP_lo)) * (C - BP_lo) + I_lo
   

   where C is the concentration, BP_lo/BP_hi are the breakpoint limits, and I_lo/I_hi are the AQI index limits.
4. Compute overall AQI as the maximum sub-AQI across all pollutants.
5. Identify dominant pollutant: the one with the highest sub-AQI.
6. Map AQI to health category:
   • 0–50: Good
   • 51–100: Moderate
   • 101–150: Unhealthy for Sensitive Groups
   • 151–200: Unhealthy
   • 201–300: Very Unhealthy
   • 301–500: Hazardous

Output / side effects

Print a table of per-pollutant AQI:

| Pollutant | Concentration | Sub-AQI | Category                      |
|-----------|----------------|---------|-------------------------------|
| PM2.5     | 45 µg/m³       | 120     | Unhealthy for Sensitive Groups |
| PM10      | 120 µg/m³      | 95      | Moderate                      |
| O3        | 72 ppb (8h)    | 130     | Unhealthy for Sensitive Groups |

Then summarize:

• Overall AQI: 130
• Category: Unhealthy for Sensitive Groups
• Dominant pollutant: O3

Include a note: This is the US EPA AQI scale. The EU CAQI (Common Air Quality Index) and AirNow regional scales use different breakpoints; results may differ.

Safety / constraints

• Validate that concentrations are non-negative; reject or warn on negative inputs.
• If averaging period is mismatched (e.g., 1-hour PM2.5 instead of 24-hour), warn the user that the result may not align with regulatory standards.
• Do not perform any external API calls in this skill — all computation is local and deterministic.