<prompt> In Indoor air pollution, carbon monoxide is produced by -Combustion equipmentStoveGas heatersAll of the above  <response>: 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 fueltobacco combustion. Combustion equipment, stoves, gas heaters all act as a source of carbon monoxide. Parks Textbook of Preventive and Social Medicine, 25th edition, Page No. 796 