Levels and determinants of indoor carbon monoxide (CO) pollution were characterised in a pilot sample of households in Bogota, Colombia, in which natural gas appliances (NGA) were frequently used. Real-time CO concentration measurements were conducted using Langan T15 electrochemical cells in kitchen and living rooms, at 73 homes. Results show that the use of NGA has a direct impact on indoor air quality with CO concentrations ranging between 5 and 150 parts-per-million. In 14 out of the 73 homes, CO concentrations were above the World Health Organization standards during at least 10% of the day. This is a matter of concern for local public health authority since the number of reported cases of CO involuntary intoxications in the city has significantly increased since 2008. Evidence presented hereby has important implications in regard to NGA installation standards and housing polices (especially in the case of low income dwelling). It urges to involve healthy-house concepts in building codes, to prevent inadequate indoor air quality and to improve people living conditions.