What environments can lead to carbon monoxide poisoning?

Carbon monoxide poisoning occurs when carbon monoxide, a colorless, odorless gas, builds up in enclosed spaces, leading to harmful effects on human health. The correct choice highlights the risk associated with encapsulated spaces that have exhaust fumes, such as garages, poorly ventilated homes, and vehicles that are left running indoors. These environments can trap carbon monoxide, preventing it from dissipating and allowing dangerous levels to accumulate.

In contrast, well-ventilated areas, open-air fields, and fresh air ventilation systems typically facilitate the dispersion of gases, including carbon monoxide. Proper ventilation helps to reduce the concentration of this harmful gas, significantly lowering the risk of poisoning. Therefore, environments that are not adequately ventilated and contain sources of carbon monoxide, like exhaust fumes, pose the greatest threat.