Explainer: How is air quality measured? What does 'AQI 1,000' mean
After Diwali 2025, Delhi's air quality took a nosedive, with some reports showing AQI numbers shooting past 1,000—one viral screenshot even showed 1,975 at Mandir Marg around 1:30am.
Social media was flooded with images of thick smog and worried reactions about just how bad things had gotten.
Why did we see AQI numbers above 500?
Not all AQI numbers are calculated the same way.
International sites like IQAir use the US EPA method, which can show values well above 500.
But in India, the CPCB caps its scale at 500—anything above that is just called "severe."
So if you see a wild number like 1,000 online, it actually means "off the charts" by Indian standards.
What do the different AQI colors mean?
AQI (Air Quality Index) is a color-coded system that tells you how polluted the air is and what it means for your health.
The CPCB ranks air from "Good" (0-50) to "Severe" (401-500). The higher the number, the riskier it gets—especially for people with breathing or heart issues.
AQI is based on pollutants like PM2.5, PM10, NO2, SO2, CO, and ozone mixed in the air you breathe.