"There have been questions about whether CO alarm standards are protec- tive enough, especially for sensitive groups such as older adults." EPA CO is "recognized for causing permanent injury to the brain in concentrations once thought too low for concern." Rutgers University
"Exposure to low levels of carbon mon- oxide (under 30 ppm) can cause fatigue, chest pain, shortness of breath, memory loss, skin lesions, sweating, and flu-like symptoms. In the long term, exposure to low levels can cause heart disease and damage to the nervous system." NIH
"The elderly, pregnant women (and their unborn children), young infants, and those with certain pre-existing health problems are the most susceptible to health effects from CO exposure." HUD