Explainer: What to make of the variations in air quality readings

The article explains why air quality figures can look very different depending on which agency or index you check. In late October, Delhi and nearby regions were smothered in haze after Diwali, and although most monitors agreed the air was polluted, the readings for PM2.5 (tiny harmful particles) varied between government and private trackers. Experts say that differences in measurement methods and calculation standards lead to these discrepancies, but regardless of the numbers shown, any reading above the safe limit means the air is unhealthy and harmful to health.

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