Since there has been a lot of confusion around air quality index (AQI) and mass concentration, I’ve attached a simple converter from the Clean Air Initiative (CAI), an Asia-based air pollution research and advocacy group that we belong to.
There are plenty of background discussion, but basically, AQI or API is a local, China and HK-based number that is made up and based on its own local standard. So, what is a 50, or “Class I – Excellent” may actually be a worse classification back in your home country. So, most experts always recommend you either get the data in mass terms (micrograms per m3) or convert the API.
This simple excel program lets you do that. Once you do that, you can interpret the numbers using the standard of your choice. Common international standards can be found here.