New Delhi, Oct 17: Delhi's air quality, which has already entered the red zone, may trigger an increase in parking fees by up to four times across the city in the next few days, officials said on Tuesday. The measure, if required, will be enforced under the Environment Pollution (Prevention and Control) Authority's (EPCA) Graded Response Action Plan, under which a series of measures will be taken based on the severity of air pollution during winter months. Measures under the "very poor" and "severe" categories of the plan came into force on Tuesday, under which the Badarpur Thermal Power Station has been shut and diesel-run generators (digi sets) banned in Delhi, among other actions. EPCA Chairman Bhure Lal and Member Sunita Narain announced the decision following a review meeting here. "DG sets will be banned only in Delhi, conditional to air quality index reaching to very poor or severe," said Narain. Narain said parking fees could be hiked in Delhi, despite the fact that a parking policy was still being worked out, if air pollution aggravated further. In case it touched alarming proportions, "cars will have to be off the roads", she added. The environment body has also advised the residents of Delhi-NCR to use face masks whenever possible. It has also raised concerns over the existing landfill sites in the capital.