Explained: Diwali celebrations coincide with worsening air. Here’s how to stay safer

Diwali celebrations in South Asia, especially northern India, coincide with the return of hazardous winter air.

AQI

Air Quality Index, a scale turning pollution measurements into health warning categories like 'poor,' 'very poor' and 'severe'

HEPA filter

High-efficiency particulate air filter used in purifiers to trap fine particles

N95/N99 masks

Particle respirator masks designed to filter out at least 95% or 99% of airborne particles, respectively

Clean air delivery rate

A measure of the volume of filtered air an air purifier supplies

Fine particle pollution

Tiny airborne particles that can be inhaled deep into the lungs, worsened by traffic, factories, dust and burning