According to ASHRAE, what is the maximum allowable concentration of carbon monoxide for continuous 24-hour exposure?

The correct answer is based on the guidelines set by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), which provide safety standards for indoor air quality, particularly concerning the levels of carbon monoxide (CO). ASHRAE considers 9 parts per million (PPM) as the maximum allowable concentration for continuous exposure over a 24-hour period. This level is established to mitigate potential health risks associated with carbon monoxide, which can be harmful, particularly in enclosed spaces where it can accumulate.

Continuous exposure to higher concentrations of CO can lead to symptoms of carbon monoxide poisoning, which include headaches, dizziness, confusion, and, in extreme cases, can be fatal. By establishing a lower threshold, ASHRAE aims to ensure that indoor environments remain safe and comfortable for occupants, emphasizing the importance of adequate ventilation and CO detection systems in heating and cooling installations.

In summary, the choice of 9 PPM reflects a commitment to minimizing health risks associated with long-term exposure to carbon monoxide indoors, ensuring the well-being of individuals in such environments.