What is the ASHRAE suggested maximum 24-hour exposure to carbon monoxide in room air?

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) provides guidelines for safe indoor air quality, including recommendations for exposure to carbon monoxide (CO). The suggested maximum 24-hour exposure limit for carbon monoxide in room air is set at 9 parts per million (ppm). This level is designed to protect individuals from the potentially harmful effects of CO exposure, especially since carbon monoxide can be particularly dangerous because it is colorless, odorless, and can lead to serious health issues, including poisoning.

Choosing 9 ppm reflects a balance between allowable limits for indoor air quality and the need for safety, recognizing that prolonged exposure to even low levels of CO can lead to health consequences. Other suggested amounts exceed safe exposure guidelines, indicating increased risks to health and safety that ASHRAE aims to mitigate with this standard.