`elwood_spatial.air_quality`

Domain-specific utilities for air quality monitoring. Provides EPA-compliant AQI bin presets and PM2.5 ↔ AQI conversion functions based on 40 CFR 58 Appendix G breakpoints.

Presets

`AQI_BINS`

Standard EPA 6-bin AQI categories.

Bin	Range	Category
0	0 – 50	Good
1	51 – 100	Moderate
2	101 – 150	Unhealthy for Sensitive Groups
3	151 – 200	Unhealthy
4	201 – 300	Very Unhealthy
5	301 – 500	Hazardous

`AQI_MODIFIED_BINS`

Modified 12-bin percentile categories from the paper, with transition zones at category boundaries.

Bin	Range	Label
0	0 – 44.9	G
1	45 – 55.9	GM
2	56 – 95	M
3	95.1 – 105.9	MUSG
4	106 – 145	USG
5	145.1 – 155.9	USGU
6	156 – 195	U
7	195.1 – 210.9	UVU
8	211 – 290	VU
9	290.1 – 320.9	VUH
10	321 – 500	H
11	501 – 99999	BH

`pm25_to_aqi(pm25)`

Convert a PM2.5 concentration (µg/m³) to an AQI value using EPA breakpoints.

Parameter	Type	Description
`pm25`	`float`	PM2.5 concentration

Returns int | None. Returns None for None input, 0 for negative values.

from elwood_spatial.air_quality import pm25_to_aqi

pm25_to_aqi(35.0)   # => 100
pm25_to_aqi(55.4)   # => 150

`aqi_to_pm25(aqi)`

Inverse conversion — AQI value to PM2.5 concentration.

Parameter	Type	Description
`aqi`	`float`	AQI value

Returns float | None. Rounded to 1 decimal place.