Carbon monoxide (CO) poisoning in the home is a frequent health problem during the winter months in Ankara and during the year 1992, 277 cases of acute CO intoxication were recorded. The sources of poisoning were mainly from bucket coal stoves and water heaters. A study was conducted in order to find the exact mechanism of high indoor CO pollution. It was found that the most important cause of CO poisoning, resulting from the use of bucket coal stoves, was malfunctioning of chimneys due to blockage with tar, cement or bricks. Water heaters, on the other hand, produced problems when they were fixed in a small bathroom without ventilation holes and malfunctioned due to lack of regular maintenance.