Delhi's toxic winter air is back - is the Indian capital prepared for pollution?

There are two cardboard boxes in Meenu Rana's living room in Delhi. One is filled with Diwali decorations and twinkling lights. The other holds air purifiers.

The mornings have already started feeling stuffy. It will get worse in the coming days, so it's better to be prepared," says the 43-year-old teacher.

She is not alone. Every year, as winter and the festive season approach, residents of India's capital begin preparing for something far less celebratory: months of breathing polluted air.

Delhi and its satellite cities record some of the world's highest pollution levels through the year. But as winter sets in, the air often becomes unbearable.

Falling temperatures and slower winds trap pollutants close to the ground instead of allowing them to disperse. Smoke from crop residue burning in neighbouring states adds to emissions from vehicles and factories, as well as construction dust. Firecrackers used during festivals often worsen air quality.