What is the acceptable percentage of carbon monoxide (CO) in a sample of flue gas?

The acceptable percentage of carbon monoxide (CO) in a sample of flue gas is 0.04%. This low concentration is critical for safety and efficiency in combustion processes. At 0.04%, the levels of CO are generally considered safe for indoor air quality, suggesting that the combustion appliance is functioning well and that there is adequate ventilation to dissipate any harmful gases.

Higher levels of CO, as indicated by the other options, would signify incomplete combustion, which not only reduces the efficiency of heating appliances but also increases the risk of toxic exposure. This is particularly important in residential and commercial settings where a buildup of CO can pose serious health risks. Understanding the acceptable limits is essential for maintaining safety standards in appliance operation and ensuring compliance with relevant regulations.