Absolutely, carbon monoxide could be entering the vehicle due to a faulty exhaust system. Carbon monoxide is a poisonous gas that causes headache, dizziness, nausea and can render the victim unconscious, it can also be fatal. The vehicle should be inspected asap, and not be driven unless absolutely necessary, if it is driven all the windows should be open. If a person has any of the symptoms of carbon monoxide poisoning it would be advisable to seek a medical evaluation.
funny as it may sound there might be a dead mouse in there happened to me
A rotten egg odor may indicate a dead rodent or animal in or near the ventilation system, whether in a house or car.
Leak in exhaust system perhaps exhaust manifold being sucked in through air intake (grid at lower end of windshield)
There is a very small leak in the heater core that is collecting in the vent system and is evaporating out when you turn the heater on. The smell is from the antifreeze in the water.
No, it won't carry the required amount of air. A vent is usually 1.5 inch and an exhaust is 4 or 5 inch.
One cooling fan, one intake vent and one exhaust vent.....
Exhaust fans are very important for industries, especially those which manufacture or work with chemicals. Exhaust fans help by propelling outward the dangerous fumes of chemicals. You will also need a source of fresh air, such as an air vent or window in order to create air circulation.
Stopped up vent or improperly installed vent.
An air admittance vent is a mechanical sewer vent which allows air to enter into the sewage system but does not allow exhaust of sewer gases.
You probably have mold in the heater vent ducting.
Commercial or residential and what manufacturer
I would reccomend that you have an external vent for the air to go thru and not just into the attic alone.