What is the primary danger of driving a commercial vehicle with severe diesel exhaust leaks entering the passenger or driver cab?

1. Carbon monoxide and toxic diesel particulates cause dizziness, headache, loss of consciousness, and fatal asphyxiation
2. It is harmless because diesel exhaust contains no carbon monoxide
3. It is a problem only when the vehicle is stationary with the engine idling
4. It affects passengers in the saloon but not the driver in the cab