What percentage of Carbon Monoxide will produce symptoms in several hours?

The correct choice indicates that a concentration of 0.02% Carbon Monoxide (CO) in the air can begin to produce symptoms after several hours of exposure. This level of CO is significant enough that even a small percentage can lead to health-related issues, particularly for individuals who are at greater risk, such as those with preexisting health conditions.

Carbon Monoxide is a colorless, odorless gas that is harmful when inhaled, as it can inhibit the blood's capacity to carry oxygen. Symptoms typically start with the presence of CO in non-life-threatening amounts but can escalate with prolonged exposure. At the 0.02% level, symptoms like headache, dizziness, and fatigue can manifest slowly. This serves as a reminder of the risks associated with even low-level exposure to Carbon Monoxide, emphasizing the importance of monitoring indoor air quality, especially in enclosed spaces.

Other percentages listed are either too low or too high to create symptoms in that timeframe. For example, levels below 0.02% are often considered non-symptomatic under normal exposure conditions, while higher concentrations would produce more immediate and severe health effects.