a common joke among tech/science folks is "The great thing about standards is that there are so many of them" and this applies to AQI as well - different countries have different versions of the AQI "standard" so when checking readings from a web site, app or device check which AI standard is being used
also the AQI rating is calculated based on many different aspects of air quality, including levels of PM2.5, PM10, NO2, O3, CO and SO2. In some discussions and news reports the main interest is PM2.5 levels as a significant health issue so when looking at a reported figure it is important to know if this is an AQI or a PM2.5 measurement - for example in Bang Rak in Bangkok at the moment the AQI is 61 and the PM2.5 is 17, both considered "moderate" on their respective scales (US AQI), but if the AQI is confused with a PM2.5 then 61 is a significantly more "unhealthy" PM2.5 level than 17
and when considering PM2.5 levels, again different countries have set different "target" levels - often incorrectly referred to in the press and government announcements as "safe" levels - 10, 20, 33, 50 etc. In the past Thailand used to use 50 but most recent reports seem to use 33, still a long way from the WHO recommended target or the targets set in many other countries.
and if you do get yourself a home air purifier with a HEPA filter put it in the kitchen and watch it go ballistic as you cook dinner!
and there was an article in the Bangkok Post recently about converting the Erawan Shrine from using wax candles to electric ones to reduce the PM2.5 levels in the area, something already done in Singapore and Taiwan!