A Central Pollution Control Board official said the AQI entered the "severe plus" or "emergency" category late Thursday night, the first time since January this year. If the air quality persists in the "severe plus" category for more than 48 hours, emergency measures such as odd-even car rationing scheme, banning entry of trucks, construction activities and shutting down schools are taken under the Graded Response Action Plan, the official said. The hazardous pollution levels forced a number of people to miss morning walks and other activities. Shubhomoy Sikdar, a Delhi-based journalist, said the pollution levels gave him a throat infection and he had to skip his daily sports session. Amanpreet Singh, a resident of Jangpura, said he has been avoiding morning and evening walks and preferring to stay indoors. The number of masked faces continued to grow as the city remained shrouded in pungent haze for the fourth consecutive day. -- PTI