New Delhi, June 17 -- Air pollution and urban heat cancel out 88 per cent of Delhi's 'thermally comfortable hours' in a year, according to a new study conducted by CEPT University, Ahmedabad and Respirer Living Sciences.

While the city of Delhi experiences about 2,210 thermally comfortable hours in a year defined using an outdoor temperature range of 18 degreed C to 31 degreesC-an overwhelming 1,951 of those hours (88 per cent) also coincide with poor air quality (an Air Quality Index above 150), a statement by CEPT noted.

That leaves just 259 hours in a year, or about three per cent of the total annual hours, where residents can enjoy both clean air and comfortable temperatures, conditions necessary for safe and effective natural venti...