Understanding Carbon Monoxide Exposure: Outdoor Risks & Prevention

Carbon Monoxide Poisoning.

Have you ever passed by an idling car while jogging or strolling? You might not realize that these vehicles spew carbon monoxide, and in older or malfunctioning cars, the carbon monoxide output can be alarmingly high.

One of the challenges with carbon monoxide poisoning is its unpredictability - its symptoms can appear immediately, after a quarter of an hour, or even days later. This makes it tough for individuals to associate their symptoms with exposure to this toxic gas from nearby cars, especially aged ones or during still weather.

Not only vehicles but any motor running or idling on gasoline - generators, boats, lawnmowers, leaf blowers - emits carbon monoxide. If you smell engine exhaust, it's a sign that carbon monoxide is present.

Studies have indicated that even the slightest exposure to carbon monoxide is detrimental to your health. Health contributor Ted from Bangkok highlighted this fact years ago when he shared a story on Earth Clinic about an elderly man in India who suffered a stroke and slipped into a coma following a walk. He emphasized that strokes and heart attacks due to carbon monoxide poisoning are frequently under-reported, especially in regions with high vehicle pollution.

More recently, the writer of this article experienced symptoms of carbon monoxide poisoning after exposure to exhaust from two idling delivery trucks. Symptoms like a dull headache, nausea, extreme fatigue, and brain fog set in, and though the headache subsided quickly, the full recovery took two days.

Despite the perilous nature of carbon monoxide, outdoor exposure to this lethal gas is not well-researched. This gap is concerning as vehicle emissions contribute significantly to outdoor pollution. High concentrations of carbon monoxide can lead to serious health problems, yet it's an overlooked aspect in medicine.

It's crucial to recognize carbon monoxide sources and their associated risks to avoid outdoor exposure to this deadly gas. Whenever possible, steer clear of areas with high vehicle pollution and ensure proper maintenance of your home and vehicles. This proactive approach can safeguard your health and well-being.

Understanding Carbon Monoxide?

Carbon monoxide is a colorless, tasteless, and odorless gas, produced when fossil fuels burn. It's a combination of a carbon atom and an oxygen atom, hence the abbreviation - CO. This gas is slightly lighter than air, with a molar mass of 28.0 compared to the air's average molar mass of 28.8.

Termed as the "silent killer," carbon monoxide is dangerous as its effects go unnoticed. Individuals often realize the exposure only when symptoms set in, which can be hours or even days later. This trait makes it a hazardous gas, as it can lead to severe health issues without warning.

What is Carbon Monoxide Poisoning?

When carbon monoxide, a gas emitted by burning fossil fuels, accumulates in the bloodstream, it leads to carbon monoxide poisoning. Everyone is susceptible to CO poisoning when exposed to high concentrations. The sources can be varied - faulty heating systems, gas stoves, fireplaces, and vehicle exhausts.

Upon inhaling carbon monoxide, it replaces the oxygen in red blood cells, impeding oxygen supply to your body's tissues. The scary part about inhaling even a tiny amount of CO is that it's over 200 times more attractive to your blood's hemoglobin than oxygen. (1) This implies that your blood can rapidly lose its oxygen-carrying capacity, leading to tissue damage and organ failure.

CO poisoning can exacerbate any existing medical condition and poses a grave risk to the elderly, children, and individuals with prior respiratory or heart conditions. Symptoms can range from headache, dizziness, nausea, and confusion to loss of consciousness. In extreme cases, CO poisoning can be lethal.

Immediate medical help is essential if you suspect CO poisoning in yourself or others.

Why Small Amounts and Small Doses of Carbon Monoxide Are Bad for You

Carbon monoxide is a poisonous gas that forms carboxyhemoglobin (COHb) when it binds with hemoglobin in the bloodstream, preventing the latter from carrying oxygen. The concentration of inhaled carbon monoxide determines the amount of COHb produced. The reduction of available oxygen to the tissues leads to chemical asphyxia and hypoxia, causing oxygen deprivation to the organs.(2)

Carbon monoxide can also bind to other molecules, disrupting normal physiological processes like mitochondrial function and inducing oxidative injury. (3)

Even in small amounts, carbon monoxide can have major health consequences. Preventive measures like ensuring proper ventilation in enclosed spaces and regular maintenance of heating and cooking equipment can mitigate exposure to this gas.

Toxicity Levels of CO

The bodily damage from carbon monoxide poisoning depends on the concentration of the inhaled gas. Concentrations as low as 667 parts per million (ppm) can cause seizure, coma, and fatality by converting up to 50% of the body's hemoglobin to carboxyhemoglobin.(4)

Structures like the brain and eyes that demand high oxygen are at greatest risk of CO exposure due to susceptibility to hypoxia or oxygen deprivation.

In 2011, vehicles accounted for 52% of carbon monoxide emissions in the US, as per a now-removed EPA report. Based on the engine's condition, older gasoline engines without catalytic converters can have tailpipe concentrations as high as 30,000 to over 100,000 ppm.  (5)

Even low carbon monoxide levels from vehicle emissions can significantly impact health, especially for vulnerable populations.

How Does Vehicle Carbon Monoxide Affect the Air We Breathe?

Despite reduced carbon monoxide emissions due to EPA emission standards, a single vehicle with high carbon monoxide output can still pollute the air. (7)

Why Are Vehicle Exhaust Systems Hazardous?

Gasoline engines of internal combustion produce high carbon monoxide concentrations. A well-tuned engine can emit over 30,000 ppm of CO before the catalytic converter. Any leaks in the exhaust can lead to escape of carbon monoxide before conversion to harmless CO2, making it a risk. (7)

If you're near a car or truck leaking high concentrations of carbon monoxide, you'll inhale a dangerous amount of this gas within a few breaths. Luckily, newer vehicles are equipped with catalytic converters that convert carbon monoxide to carbon dioxide, lowering its concentrations. However, older vehicles and those with exhaust system leaks can release high carbon monoxide amounts, putting anyone nearby in harm's way.

Two Critical Questions: How Does Inhaling Carbon Monoxide Affect Health?

When it comes to inhaling carbon monoxide, even brief exposure to high concentrations can have serious health consequences. This leads to two critical health questions:

  1. What happens if you inhale a high concentration of carbon monoxide while walking outside?
  2. What happens when carbon monoxide gets into your eyes?

Carbon monoxide poisoning primarily affects organ systems that are highly dependent on oxygen, such as the brain, heart, eyes, and central nervous system. (8) Symptoms of carbon monoxide poisoning can occur immediately or have a delayed onset and are frequently mistaken for the flu, food poisoning, or gastroenteritis.

Headaches are the most common symptom of short-term carbon monoxide poisoning, but many others can also occur, such as dull frontal headaches, fatigue, sudden onset of depression, tinnitus, brain fog, weakness, dizziness, nausea, shortness of breath, confusion, arrhythmias, memory issues, movement problems, and blurred vision. Even small amounts of carbon monoxide can cause symptoms. (9)

Symptoms From Short-Term Exposure to Carbon Monoxide

  • Dull, Frontal Headache
  • Immediate Fatigue
  • Depression, Sudden Onset
  • Tinnitus
  • Brain Fog
  • Weakness
  • Dizziness
  • Nausea
  • Shortness of breath
  • Confusion
  • Arrhythmias
  • Memory Issues
  • Movement Problems
  • Tinnitus
  • Blurred vision

























Less Common Symptoms of CO Poisoning

Less common symptoms of acute carbon monoxide poisoning include:

  • myocardial ischemia
  • atrial fibrillation
  • pneumonia
  • pulmonary edema
  • high blood sugar
  • lactic acidosis
  • muscle necrosis
  • acute kidney failure
  • skin lesions
  • visual and auditory problems (9) (10) (11) (12)

Complications From Carbon Monoxide Exposure

Depending on the amount of exposure, carbon monoxide poisoning can have serious complications, including:

  • Brain damage, including strokes
  • Damage to your heart, including heart attacks
  • Fetal death or miscarriage
  • Death

Carbon monoxide exposure may lead to a significantly shorter life span due to heart damage. (13)

Carbon Monoxide Tolerance Levels

Several factors affect carbon monoxide tolerance level for any person, including:

  • Activity level rate of ventilation pre-existing cerebral issues
  • Pre-existing cardiovascular disease
  • Cardiac output
  • Anemia
  • Sickle cell disease and other hematological disorders,
  • Barometric pressure
  • Metabolic rate (14)

Delayed Neurological Complications from Carbon Monoxide Poisoning

One of the major concerns following carbon monoxide poisoning is the delayed neurological complications that can occur anywhere from 2 to 40 days after exposure to Carbon Monoxide.

Problems may include the following:

  • Short-term memory loss
  • Dementia
  • Amnesia
  • Psychosis
  • Irritability
  • Strange Gait
  • Speech Disturbances
  • Parkinson's Disease-like Syndromes
  • Cortical Blindness
  • Depression in those who did not have pre-existing depression (15)

Advanced age and initial neurological abnormalities may increase the chance of developing delayed symptoms. (16)

The time it takes to recover from carbon monoxide poisoning entirely depends on the amount of carbon monoxide gas inhaled.

The half-life of carbon monoxide without using oxygen is 320 minutes—more than five hours to reduce levels by half. If you breathe fresh air, it will take five hours to get half the carbon monoxide out of your system. It will take another five hours to cut that level in half.

Suppose there is just one instance of high ppm carbon monoxide gas inhalation from a passing car, for example. In that case, symptoms may resolve anywhere from a few hours to a week of inhalation as long as you are not subjected to further incidences of CO poisoning. (18)

High-level carbon monoxide poisoning is often treated with high-flow oxygen for as long as it takes to replace the carbon monoxide attached to hemoglobin with oxygen. Severe carbon monoxide poisoning requires time in a hyperbaric oxygen chamber.

Warning: Paint and Varnish Solvents Can Also Create Carbon Monoxide

Methylene chloride, a solvent commonly found in paint and varnish removers, can break down into carbon monoxide when inhaled. Exposure to methylene chloride can cause carbon monoxide poisoning.

Always use caution when working with paint solvents indoors—open windows. (19)

How Can I Protect Myself From Vehicular Carbon Monoxide Poisoning?

  • Move out of the area of any idling car, truck, or boat if you start to feel light-headed or nauseous.
  • Wear protective eyewear.

What Can I Do to Clear My Body from CO Poisoning?

It takes very little carbon monoxide in the air you breathe to get CO poisoning. Unfortunately, it takes a lot of oxygen to get rid of it, which is the traditional CO poisoning treatment.

Hyperbaric Oxygen Chamber

For severe cases of CO poisoning, oxygen is administered in a hyperbaric chamber. This is a tube where the patient lies in and breathes 100% oxygen at high pressure. Using a hyperbaric oxygen chamber, you can reduce the elimination half-life of carbon monoxide to about 20 minutes. (20)

Hydrogen-Rich Saline Solutions

Another treatment that has been frequently studied in animals for acute CO poisoning is hydrogen-rich saline.  The saline is an antioxidant, non-toxic, convenient, and safe to use.  It is commonly used in Japan for metabolic disorders. (21)

Natural Remedies for Carbon Monoxide Poisoning

Because hyperbaric oxygen therapy is only available in severe carbon monoxide poisoning cases, it is an excellent idea to know your options for suspected short-term but high-concentration events outdoors.

Supplemental Oxygen Can


Shirley M. from Sedona made a fantastic suggestion to keep supplemental oxygen called Boost O2 in your home and car, as you will read in the feedback section below.

Read about Boost O2 on Amazon here.



Take antioxidants to control the potential damage from carbon monoxide poisoning. Three of the most potent antioxidants are:

  • Astaxanthin
  • Vitamin E
  • Vitamin C

Home Remedies

Any supplement or natural remedy traditionally used for stroke and heart disease prevention might be helpful if carbon monoxide poisoning from short-term exposure is suspected.

These remedies include:

  • Cayenne Pepper
  • Nattokinase
  • Baby Aspirin
  • Hydrogen Peroxide Inhalation or Therapy

Take upon the first sign of CO poisoning.

How Fast Does Carbon Monoxide From Vehicles Dissipate in the Air Outside?

How quickly carbon monoxide dissipates outside depends on how much wind there is.

On a windless day, a blast of high ppm (parts per million) carbon monoxide from a tailpipe can hover in the area for more than just a few seconds.

Dangerous levels of carbon monoxide can accumulate anywhere near an idling motor vehicle or boat.

Can I Get Carbon Monoxide Poisoning Through My Eyes?

Yes. The brain and eyes are most at risk upon exposure to this gas due to these structures' enormous oxygen demands. (22)

How Do I Protect My Eyes from the Effects of Carbon Monoxide Gas?

Wear protective eye gear such as sunglasses or glasses when you are near any active or idling gasoline-based engine where you can see or smell exhaust. If you can smell engine exhaust, carbon monoxide is present.

When to Seek Medical Help

Call 911, move to a source of fresh air, and seek prompt medical help if you suspect severe CO poisoning, are feeling dizzy, light-headed, weak, or nauseated.

































  • Today, most cars have a catalytic converter, which transforms carbon monoxide into harmless carbon dioxide before it comes out of the tailpipe. The problem is with older cars that do not have these converters or vehicles with their exhaust systems.
  • When there is any carbon monoxide in the air you're breathing, your body replaces the oxygen in your red blood cells with it.

  • It only takes carbon monoxide concentrations as low as 667 ppm to cause up to 50% of the body's hemoglobin to convert to carboxyhemoglobin. This means that much lower concentrations of CO can cause damage to the body.
  • Carbon Monoxide poisoning effects are cumulative.
  • Repeated carbon monoxide exposure of any level and concentration can lead to serious health issues and even death.
  • Besides your lungs, the eyes are also entry points for this toxic gas and should be protected with eye gear. This is especially true for the sick or elderly.
  • Keep elderly and sick people away from idling vehicles and boats.
  • Carbon Monoxide poisoning symptoms can appear immediately or have a delayed onset, making it difficult to diagnose as the cause.

Continue reading below for tips from Earth Clinic readers about remedies that might help you heal from CO poisoning. If you have one to add to the list, please do not hesitate to write us!


Hoffman, R. S., G. L. Davis Jr, M. J. Wong, and M. D. Geller. "Cardiac arrhythmias and carbon monoxide." JAMA 230, no. 10 (1974): 1300-1303.:  This study examined the effects of carbon monoxide exposure on cardiac function in patients with pre-existing cardiovascular disease. The researchers found that exposure to low levels of carbon monoxide during a 90-minute car ride on a Los Angeles freeway caused EKG irregularities in 40% of the patients, indicating that even low levels of carbon monoxide from motor vehicle emissions can have a significant impact on health, especially for vulnerable populations.

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List of Remedies for Carbon Monoxide Poisoning