The concentration of carbon monoxide in concealed spaces compared to open spaces can be how much greater?

In concealed spaces, the concentration of carbon monoxide can indeed be significantly higher than in open spaces, which is why the correct answer is the greatest multiplier of concentration. This increase is primarily due to the lack of ventilation in concealed areas. When combustion occurs, carbon monoxide is produced, and in an enclosed space where airflow is limited, this toxic gas can accumulate rapidly, leading to much higher levels than what would be found in more open environments where the gas can disperse.

In particular, the reasoning behind a 50 times greater concentration highlights the serious risks associated with concealed spaces, such as attics, basements, or any areas that are not exposed to adequate airflow. These environments can trap gases, potentially reaching levels that pose significant health risks to individuals, making it crucial for fire inspectors to be aware of these dangers when assessing buildings and creating safety protocols. The other options, while they indicate elevated risks, do not capture the full potential severity of carbon monoxide accumulation in concealed spaces as effectively as the highest value.