Nebulo's data all conform to US EPA AQI standards. See below for the specific description of each country.
Singapore & Hong Kong
Singapore and Hong Kong both offer 1-hour PM2.5 readings in ug/m3. We take these readings and convert them to US EPA AQI using PM2.5 as the pollutant.
Singapore Data source: National Environment Agency - Haze Updates, 1-hr PM2.5 Readings
Hong Kong Data source: Environmental Protection Department - Air Quality Health Index (AQHI), Pollutant concentrations