Colour Scales and AQIs – Earthsense

What are colour scales?

This article explains the colour scale system used by EarthSense’s MyAir platform for air quality visualisation. It covers EarthSense’s proprietary scales as well as regulatory-based scales from Defra, the EU, and the US EPA, providing a comprehensive guide to how different pollutant levels are represented in MyAir.

With colour-coded bands for pollutants like NO₂, O₃, SO₂, PM₁₀, and PM₂.₅, users can quickly interpret air quality data based on region-specific or global standards. Tables with sample colours help illustrate each scale, enabling users to make informed decisions based on pollutant levels.

Air Quality Indices

MyAir also provides AQIs to represent air quality data, enabling quick interpretation of pollutant levels. When using the location page, you can choose from EarthSense's custom colour scales or regulatory-based scales.

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Showing hourly data is beneficial as it helps tease out pollution hotspots and exceedances. However, not all AQIs are designed to work for hourly data. To keep things consistent, we sometimes apply non-hourly thresholds on hourly data.

EarthSense Colour Scales

EarthSense Hourly (National)

This colourscale is available to use on data from the EarthSense MappAir UK hourly model.

Band Name	AQI Band	NO₂ (µg/m³) 1-hour	PM₂.₅ (µg/m³) 1-hour	Colour	Bluescale Version	RGB	Hex
Exceptionally low for the UK	0	0	0			(156, 255, 156)	#9CFF9C
Very low for the UK	1	5	4			(49, 255, 0)	#31FF00
Relatively low for the UK	2	15	8			(49, 207, 0)	#31CF00
Moderately low for the UK	3	25	12			(255, 255, 0)	#FFFF00
Moderate for the UK	4	35	16			(255, 207, 0)	#FFCF00
Moderately high for the UK	5	45	20			(255, 154, 0)	#FF9A00
Higher for the UK	6	55	24			(255, 92, 1)	#FF5C01
High for the UK	7	70	30			(255, 0, 0)	#FF0000
Exceptionally high for the UK	8	100	40			(153, 0, 0)	#990000
Extremely high for the UK	9	150	70			(100, 0, 43)	#64002B

EarthSense Hourly (Global)

This colourscale is available for data from the the EarthSense MappAir global hourly model.

Band Name	AQI Band	NO₂ (µg/m³) 1-hour	O₃ (µg/m³) 1-hour	SO₂ (µg/m³) 1-hour	PM₁₀ (µg/m³) 1-hour	PM₂.₅ (µg/m³) 1-hour	Colour	Bluescale Version	RGB	Hex
Very low	0	0	0	0	0	0			(156, 255, 156)	#9CFF9C
Very low	1	15	34	5	17	12			(49, 255, 0)	#31FF00
Relatively low	2	30	67	15	34	24			(49, 207, 0)	#31CF00
Relatively low	3	40	101	30	51	36			(255, 255, 0)	#FFFF00
Moderate	4	50	121	50	59	42			(255, 207, 0)	#FFCF00
Moderate	5	70	141	80	67	48			(255, 154, 0)	#FF9A00
Higher	6	100	161	120	76	54			(255, 92, 1)	#FF5C01
Higher	7	150	188	200	84	59			(255, 0, 0)	#FF0000
Relatively high	8	200	214	300	92	65			(153, 0, 0)	#990000
Extremely high	9	300	241	500	101	71			(100, 0, 43)	#64002B

EarthSense Annual

This colourscale is for annualised modelled data.

Band Name	NO₂ (µg/m³) Annual	PM₂.₅ (µg/m³) Annual	Colour	RGB	Hex
Exceptionally clean	0	0		(68, 1, 84)	#440154
Very clean	4	2		(72, 36, 117)	#482475
Very lightly polluted	8	3		(64, 67, 135)	#404387
Lightly polluted	12	5		(52, 95, 141)	#345F8D
Light to moderately polluted	16	6		(41, 120, 142)	#29788E
Moderately polluted	20	8		(32, 144, 141)	#20908D
Moderately to heavily polluted	24	9		(34, 168, 132)	#22A884
Heavily polluted	28	11		(67, 191, 112)	#43BF70
Very heavily polluted	32	12		(122, 210, 81)	#7AD251
Extremely polluted	36	14		(188, 223, 39)	#BCDF27
Exceptionally polluted	40	15		(253, 231, 37)	#FDE725

Regulatory-Based Colour Scales

DEFRA (UK)

Available here.

Band Name	NO₂ (µg/m³) 1-hour	O₃ (µg/m³) 8-hour rolling	SO₂ (µg/m³) 15-min	PM₁₀ (µg/m³) 24-hour	PM₂.₅ (µg/m³) 24-hour	Colour	RGB	Hex
Low	0	0	0	0	0		(156, 255, 156)	#9CFF9C
Low	68	34	89	17	12		(49, 255, 0)	#31FF00
Low	135	67	178	34	24		(49, 207, 0)	#31CF00
Moderate	201	101	267	51	36		(255, 255, 0)	#FFFF00
Moderate	268	121	355	59	42		(255, 207, 0)	#FFCF00
Moderate	335	141	444	67	48		(255, 154, 0)	#FF9A00
High	401	161	533	76	54		(255, 92, 1)	#FF5C01
High	468	188	711	84	59		(255, 0, 0)	#FF0000
High	535	214	888	92	65		(153, 0, 0)	#990000
Very High	601	241	1,065	101	71		(100, 0, 43)	#64002B

EU AQI

Available here.

Band Name	NO₂ (µg/m³) 1-hour	O₃ (µg/m³) 1-hour	SO₂ (µg/m³) 1-hour	PM₁₀ (µg/m³) 24-hour	PM₂.₅ (µg/m³) 24-hour	Colour	RGB	Hex
Good	0–10	0–60	0–20	0–15	0–5		(80, 240, 230)	#50f0e6
Fair	11–25	61–100	21–40	16–45	6–15		(80, 204, 170)	#50ccaa
Moderate	26–60	101–120	41–125	46–120	16–50		(240, 230, 65)	#f0e641
Poor	61–100	121–160	126–190	121–195	51–90		(255, 80, 80)	#ff5050
Very Poor	101–150	161–180	191–275	196–270	91–140		(255, 140, 0)	#960032
Extremely Poor	>150	>180	>275	>270	>140		(125, 33, 129)	#7d2181

US EPA AQI

Available here.

Band Name	NO₂ (µg/m³) 1-hour	O₃ (µg/m³) 1-hour	SO₂ (µg/m³) 1-hour	PM₁₀ (µg/m³) 24-hour	PM₂.₅ (µg/m³) 24-hour	Colour	RGB	Hex
Good	0	0	0	0	0		(49, 255, 0)	#31FF00
Moderate	102	108	94	55	12		(255, 255, 0)	#FFFF00
Unhealthy for Sensitive Groups	190	139	199	155	36		(255, 154, 0)	#FF9A00
Unhealthy	679	169	487	255	56		(255, 0, 0)	#FF0000
Very Unhealthy	1222	208	355	151	-		(206, 48, 255)	#CE30FF
Hazardous	2350	425	-	251	-		(153, 0, 0)	#990000