The phenomena of carbon monoxide from the exhaust coming into the vehicle in this fashion is sometimes referred to as the station wagon effect and also occur when a boat is moving.Ĭan an Exhaust Leak be the cause of Carbon Monoxide Entering the Car? If any leaks exist, exhaust gases mixed with external air will be drawn & leak into the cabin.

In the recirculation mode, and whilst in motion, cabin pressure is less than the rear of the vehicle. Exhaust components mix with eddies (swirling air) in the near wake region and if any leaks exist in the rear vehicle surface, polluted air will be drawn into the cabin.The faster the vehicle travels, the higher the pressure differential between the cabin and the rear of the vehicle.The cabin has even less pressure than the rear of the vehicle.At the rear of the vehicle, it abruptly ends, creating a void where a low-pressure “near-wake” region forms. As the vehicle moves, it pushes the air to make way for its motion.For those interested, the pressure difference may be up to 0.5 inH2O at freeway speeds. The surface pressure is higher at the rear of the vehicle than the internal cabin.When a vehicle is in motion, a pressure differential occurs between the exterior rear and the cabin. Obstructions such as snow or debris can redirect the emissions back into the vehicle.Ĭarbon Monoxide Entering with HVAC in Recirculation Mode Neighboring station vehicle emits pollution and is drawn directly into the cabin.In this case, exhaust gas and carbon monoxide does not dilute with the outdoor environment and can be drawn into the vehicle cabin. Parked and engine is on in a quasi indoor environment with poor ventilation such as a parking structure, garage, or home garage.Downwind direction from exhaust to HVAC intake can draw exhaust gas into the cabin. If the vehicle is stationary is may draw in polluted air. Dangerous scenarios when stationary include: Air may be sucked into the vehicle by the blower - intake is usually passenger side under the windscreen. Polluted air may enter the vehicle via the HVAC system in fresh air mode. carbon monoxide accumulates in a quasi indoor environment such as a parking structure or garage and is drawn into the cabin via the fresh intake ventĬarbon Monoxide Entering with HVAC Fresh Air Mode Stationary.carbon monoxide leaks from the exhaust, exhaust manifold and engine bay.the outdoor air contains carbon monoxide due to heavy traffic or a polluted vehicle in the direct path of yours.

Carbon Monoxide may enter the cabin if:.Relief valves (air extractors) are usually placed in the trunk areas and employ one-way, self-closing flaps that open only when there is a positive pressure differential between the cabin interior and exterior.Air enters the front of the vehicle and then air leaves the vehicle cabin through the air-relief valves or through uncontrolled leak paths, which are generally a result of unintentional gaps in the vehicle body.Such a function helps eliminate external dust or pollution for increased passenger comfort.Ĭarbon Monoxide Entering with HVAC Fresh Air Mode in MotionĬarbon Monoxide can enter the cabin in fresh air mode as follows: In the recirculation mode, the recirculation door shuts the fresh air intake path so that only cabin air circulates.It will enter only from the fresh air intake that resides below the front windshield (in a typical vehicle). When the Fresh Air Mode is enabled and the fan is blowing, a positive pressure exists in the car cabin so it is less likely that outside air enters the cabin compartment through leaks or any 'unintended' pathways.

It is important to understand that a vehicle HVAC system has two operating modes. use the supply air from within the vehicle cabin).Ī typical climate control panel in a car is shown below - notice the recycle button. One can control the temperature, A/C, heating and speed of the fan including if air is to enter from the outdoors (Fresh Air) or be recycled (i.e. The HVAC is the Heating, ventilation, and air conditioning that is designed to provide comfort to passengers. The most common method of carbon monoxide entering the car is via the HVAC system, sometimes referred to as the climate control system. There are various ways carbon monoxide can leak into your vehicle. How Does Carbon Monoxide Enter the Vehicle?

Carbon dioxide poisoning from car