Air Quality

This page documents the air quality fields returned by the Pirate Weather API and provides reference tables for the regional air quality indexes used by each unit system. The index applied depends on the units parameter (or the aqiunits override), with separate indexes for US, Canadian, UK, and European standards.

Air Quality Elements

airQualityIndex

The air quality index for the requested location. The specific index format used automatically updates depending on the requested units:

• US / Default: Uses the United States Environmental Protection Agency Air Quality Index (AQI).
• CA: Uses the ECCC Air Quality Health Index (AQHI).
• UK: Uses the UK Daily Air Quality Index (DAQI).
• SI: Uses the EU Common Air Quality Index (CAQI).
• HK: (aqiunits="hk"): Uses the Hong Kong Air Quality Health Index (AQHI).
• IE: (aqiunits="ie"): Uses the Ireland Air Quality Index for Health (AQIH).
• IL: (aqiunits="il"): Uses the Israel Air Quality Health Index (AQHI).
• ID: (aqiunits="id"): Uses the Indonesia Standard Pollutant Index (ISPU).
• CN: (aqiunits="cn"): Uses the China National Ambient Air Quality Index (AQI).
• MY: (aqiunits="my"): Uses the Malaysia Air Pollutant Index (API).
• VN: (aqiunits="vn"): Uses the Vietnam Air Quality Index (AQI).

How they are calculated:

• US EPA AQI: Calculated using a 12-hour Nowcast (where the most recent hours are weighted more heavily) for PM_2.5 and PM₁₀, an 8-hour average for O₃ and CO, and a 1-hour average for NO₂ and SO₂. The overall index value matches whichever individual pollutant has the highest score.
• ECCC AQHI: Calculated using a formula based on 3-hour rolling averages of PM_2.5, O₃, and NO₂. Unlike the US index, these three values are combined into a single health risk calculation rather than just taking the maximum.
• UK DAQI: Calculated by assigning a 1–10 band to each of NO₂, SO₂, O₃, PM_2.5, and PM₁₀ based on concentration thresholds. The overall index is the maximum band value across all pollutants.
• EU EAQI: Calculated using hourly (1-hour) averages for PM_2.5, PM₁₀, O₃, NO₂, and SO₂. The overall index value represents the maximum value among all four sub-indices.
• Hong Kong AQHI: Calculated using the sum of health risk increments based on 3-hour moving averages of gaseous pollutants (NO₂, SO₂, O₃, CO) and particulate matter (PM2.5, PM10), mapped on a scale of 1 to 10+.
• Ireland AQIH: Calculated using hourly monitoring data across key pollutants (O₃, NO₂, PM_2.5, PM₁₀, and SO₂), categorized into a relative health index scale from 1 (Good) to 10 (Very Poor) based on the highest individual pollutant score. The difference between the Ireland AQIH and the UK DAQI is the Ireland AQIH uses different breakpoints for SO₂.
• Israel AQHI: Calculated using a scale that combines concentrations of major pollutants (including PM_2.5, PM₁₀, O₃, NO₂, and SO₂). Each pollutant is assigned a sub-index value, and the overall air quality index dictates the overall score. The final AQI value is calculated by subtracting the previous AQI value from 100 meaning that 100 is the highest score and -400 the lowest.
• Indonesia ISPU: Calculated by converting ambient concentrations of key pollutants (PM_{2.5, PM10, SO2, CO, O3, and NO2) into standardized sub-index values, where the maximum sub-index determines the final ISPU score.}
• China AQI: Calculated using individual air quality sub-indices (IAQI) for six standard pollutants (SO₂, NO₂, PM₁₀, PM_2.5, CO, and O₃) based on varying averaging periods (such as 24-hour averages for particles and rolling 8-hour averages for ozone). The maximum IAQI value dictates the overall AQI.
• Malaysia API: Calculated using rolling 24-hour averages for PM_2.5, PM₁₀, CO, SO₂, NO₂, and O₃. Each pollutant is assigned a sub-index value, and the highest sub-index determines the final daily API reading.
• Vietnam AQI: Calculated using individual pollutant sub-indices based on local ambient air quality standards for PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃ over specified averaging periods, with the overall index representing the highest sub-index value.

airQualityIndexMax

Only on daily. The maximum air quality index forecasted for the day, represented in the appropriate scale depending on the requested units.

airQualityIndexMin

Only on daily. The minimum air quality index forecasted for the day, represented in the appropriate scale depending on the requested units.

coConcentration

The carbon monoxide concentration represented in parts per billion (ppb).

no2Concentration

The nitrogen dioxide concentration represented in parts per billion (ppb).

ozoneConcentration

The ozone concentration represented in parts per billion (ppb).

pm25

The fine particulate matter concentration represented in micrograms per cubic meter (µg/m³).

pm10

The coarse particulate matter concentration represented in micrograms per cubic meter (µg/m³).

so2Concentration

The sulfur dioxide concentration represented in parts per billion (ppb).

Index Reference Ranges

Because each regional index uses unique breakpoints, severities, and data scales, use the respective tables below to map UI labels and alert colors based on your query's units parameter or the aqiunits override parameter.

Each index is shown in a collapsible section below. As more regional indexes are added in the future, this keeps the page manageable — expand only the index that applies to your region.