It could well be that you are breathing in air in your home that is of poorer quality than the air outside.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/air-your-home-may-be-worse-say-experts
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/times-india-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/delhi
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/indoor-air-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-quality-monitoring
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/organic-pollutants