The same concern applies to enclosed parking areas and other spaces where exhaust cannot disperse effectively.
Why opening the garage door is not enough
Opening a garage door may improve ventilation, but it does not make running an engine inside a garage safe.
The concentration of carbon monoxide depends on engine emissions, the size and ventilation of the space, airflow, and the length of time the engine runs.
Even a short period of exposure can be dangerous under certain conditions.
Never warm up a vehicle inside an attached or enclosed garage, even if the door is open. Do not leave a vehicle running while performing maintenance in an enclosed space unless the activity is conducted using appropriate professional exhaust-extraction equipment and safety procedures.
Carbon monoxide can also travel from a garage into connected living spaces.
This is especially concerning in homes where the garage shares walls or ventilation pathways with bedrooms or other occupied rooms.
What should you do instead?
If a vehicle needs to be started, move it outdoors before allowing the engine to run.
Never assume that a partially open door provides adequate protection.
Install functioning carbon monoxide alarms in appropriate locations in the home, following the manufacturer's instructions and local safety recommendations.
If a carbon monoxide alarm sounds, or if people inside a building develop unexplained symptoms, leave the area immediately and call emergency services from a safe location.
Do not re-enter until emergency responders have determined that it is safe.
3. Ignoring Unusual Exhaust Problems or a Blocked Tailpipe
A third dangerous habit is continuing to use a vehicle when its exhaust system may be damaged or obstructed.
The exhaust system carries gases away from the engine and passenger compartment. When components are damaged, the intended path for those gases may be compromised.
Problems can develop because of corrosion, physical damage, loose connections, worn seals, or faulty exhaust components.
In winter, snow can block a tailpipe. Mud, debris, or other obstructions can also interfere with exhaust flow.
A blocked exhaust outlet can create dangerous conditions, particularly when the engine continues running.
Warning signs that deserve attention
Potential warning signs of an exhaust problem include:
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An unusual exhaust smell inside the cabin.
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A change in engine or exhaust noise.
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Visible damage or corrosion around exhaust components.
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Exhaust fumes appearing near the vehicle's openings.
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A carbon monoxide alarm activating in or near the vehicle.
However, the absence of these signs does not prove that carbon monoxide exposure is impossible.
Because carbon monoxide itself is odorless, people should never rely on smell to determine whether the air is safe.
What if the tailpipe is covered with snow?
If you are driving in snowy conditions, check that the exhaust outlet is clear before starting the engine.
Snow accumulation can obstruct the tailpipe, allowing exhaust to collect beneath or around the vehicle and potentially enter the cabin.
If a vehicle becomes stuck in snow, do not simply leave the engine running for warmth without checking the exhaust outlet and ensuring that the vehicle is in a safe environment.
If exhaust cannot escape freely, turn off the engine and seek a safer solution.
If you suspect an exhaust leak, have the vehicle inspected by a qualified mechanic before continuing to use it in circumstances that could expose occupants to fumes.
Vehicle maintenance is not only about engine performance. It is also an important part of protecting the health of everyone inside.
4. Assuming Air Conditioning or Recirculation Mode Makes the Cabin Safe
Air conditioning is designed primarily to regulate temperature and humidity. It is not a substitute for carbon monoxide detection or a guarantee that exhaust gases cannot enter the cabin.
Some drivers believe that turning on the air conditioner and selecting recirculation mode completely separates the cabin from the outside environment.
That assumption is incorrect.
Vehicle ventilation systems vary, and air can enter through different pathways. Even when recirculation is selected, the system cannot guarantee protection against carbon monoxide if exhaust enters through a leak or another opening.
The air conditioner does not chemically neutralize carbon monoxide.
Likewise, a cabin air filter is not designed to reliably remove carbon monoxide from the air.
Why you may not notice the problem
Carbon monoxide does not have the distinctive smell associated with many other exhaust components.
A vehicle's cabin may feel cool, clean, and comfortable while dangerous exposure is occurring.
The absence of an unpleasant smell, visible smoke, or unusual noise should never be considered proof that the air is safe.
This is one reason carbon monoxide poisoning can be difficult to recognize.
A person may initially assume that a headache or dizziness is caused by tiredness, dehydration, hunger, or poor sleep.
If the person remains in the same environment, the exposure may continue.
What is the safer alternative?
Do not use air conditioning as a reason to sleep for prolonged periods with the engine running.
If you are tired, move to a safe place to rest where the engine can remain off.