Residents in India's northern states woke up to another day of poor air quality on Tuesday, as a layer of dense fog shrouded most of the region and pollution in the capital Delhi remained severe.India battles air pollution every winter as cold,

Toxic smog engulfed much of northern India on Monday and pollution readings in New Delhi hit their highest of this pre-winter season.

India's capital city of Delhi has virtually shut down as air pollution hit "severe plus" levels, according to Indian government officials in its pollution control authority.

Delhi's air-quality index, or AQI, shot up past 1,000 on Monday, more than five times higher than Sarajevo, the second most-polluted major city.

India's capital was left gasping this week as air pollution smog reduced visibility to near zero and raised air quality levels more than 130 times safe limits.

As authorities in Delhi-NCR enforce measures to tackle the deteriorating air quality, here's what you can do to protect yourself.

India, Delhi’s air quality index (AQI) on Tuesday morning stood at 492, which is worse than Monday’s 483. Monday’s 483 AQI was the season’s worst but Tuesday has plummeted further.