Can you get carbon monoxide poisoning from diesel semi trucks?

This is possible, but unlikely. Diesel engines detonate fuel using pressure and temperature, rather than with an artificial spark. This process operates with excessive oxygen, ensuring a much more complete combustion than what is typical in a gasoline engine. Typically, diesel exhaust contains some carbon monoxide, but the amounts are very minimal and not fatal for an otherwise healthy person. The author of this answer used to work as an over-the-road truck driver, and once had an experience where a neighboring truck was basically pumping diesel fumes straight into the sleeper vent all night. The inside of the sleeper was all hazy and the diesel odor was extremely strong, but it did not cause any health problems beyond teary eyes. It is completely possible to get carbon monoxide poisoning from a diesel engine in a road tractor. Contributing factors such as weather, temperature, and engine condition can greatly affect the chance of carbon monoxide poisoning. A good example of this is that a driver in a truck with an exhaust problem when it is cold and raining is at greater risk than the same person in the same truck on a sunny day. The reason for this is the barometric pressure holds the carbon monoxide closer to the ground and allows it to enter the truck.