A safe level of carbon monoxide in the home is from 0.5 to 5 parts per million. Levels near properly adjusted gas stoves are still safe at 5 to 15 part per million, according to the United States Environmental Protection Agency.
Carbon monoxide is a toxic gas that is both colorless and odorless. It can be safely monitored by measuring devices available in hardware stores. Symptoms of exposure to high levels of carbon monoxide include headaches, dizziness, disorientation, nausea and fatigue. Typical sources of this toxic gas include space heaters, leaking chimneys, gas water heaters, wood stoves, gas stoves, automobile exhaust and gasoline powered equipment, according to the United States Environmental Protection Agency.