Dr Randeep Guleria, Director, AIIMS, New Delhi, recommends against stepping out for morning walks. "Bad air takes a toll on everyone, especially on the heart patients, pregnant women and kids. They should avoid going out during morning and evening hours," said Dr Guleria.

"In the current situation, everyone should strictly avoid outdoor exercises as the ability to filter out or detoxify environmental agents and pollution is becoming low," he added.

Dr Piyush Goel, a pulmonologist from Columbia Asia Hospital, said that everyone must use the right kind of pollution mask while going to work or other places to survive the national capital's toxic air.

"The normal cloth mask is not so effective as it can't stop any pollutants. Special masks such as the N99 and N95 masks, though expensive, are more effective," added Dr Goel.

Since the indoor air quality also deteriorates, Dr Arunesh Kumar, chief of Chest Institute and Respiratory Medicine, Paras Hospital, cautions Delhiites to "sprinkle water in the morning and in the evening to avoid pollution from electronic items such as air conditioners."

"Using indoor plants which can purify the air inside the home is also advisable. Other than this, vaccinations are suggested to vulnerable patients, who have asthma, COPD, cardiovascular disease, cancer and those who have the transplant done," said Dr Kumar.

A layer of smog and dust particles has turned the air quality of Delhi-NCR plunging to the severe or hazardous category, making everyone cough, causing throat irritation and even spreading serious health risk.

On Friday, the Environment Pollution (Prevention and Control) Authority declared a public health emergency as the air quality will have an adverse health impact on all particularly the children.

Environmentalist Vimlendu Jha, who spoke to ANI, suggested a few steps everyone must take to increase the green cover around them, given the steep increase in pollution.

"The use of public transport must be increased. Steps to increase green cover shall be taken not only by the government but also by the citizens," said Jha.

A blanket of haze over Delhi thickened this morning with the national capital's pollution levels increasing overnight by around 50 points, taking the overall air quality index to 459.

A Central Pollution Control Board official said the AQI entered the "severe-plus" or "emergency" category late on Thursday night, the first time since January this year.