There was a slight improvement in the national capital’s air quality on Monday night, however, it continued to remain in the “poor” category, but experts said it might deteriorate in the coming days due to the toxic air coming out of a fire at Bhalswa landfill site.On Tuesday morning, the PM 10 level was at 237 and PM 2.5 level at 214, both in 'Poor' category at Lodhi Road.authorities appealed to have eco-friendly celebrations. An AQI between 0 and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.