Final answer:
Carbon monoxide (CO) is a harmful gas that can accumulate in a vehicle if there's a leak in the exhaust system, posing a risk of poisoning.
Step-by-step explanation:
The kind of gas that can accumulate inside the vehicle if there is a leak in the exhaust system is carbon monoxide (CO). Carbon monoxide is a colorless, odorless gas that is a by-product of the incomplete combustion of hydrocarbons, such as gasoline. It can be extremely harmful when inhaled, potentially leading to poisoning. Vehicles are equipped with catalytic converters that help reduce the emission of this toxic gas by converting it into less harmful substances; however, a leak in the exhaust system could allow carbon monoxide to enter the vehicle's cabin.