In Indoor air pollution, carbon monoxide is produced by -

Indoor air pollution originates from both outdoor and indoor sources, is likely to contribute to population exposure than the outdoor environment. The indoor environment represents an impoant microenvironment in which people spend a large pa of the time. Carbon monoxide, an indoor pollutant source include fuel/tobacco combustion. Combustion equipment, stoves, gas heaters all act as a source of carbon monoxide. Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 796