Understanding Carbon Monoxide Exposure: Outdoor Risks & Prevention

on Jan 19, 2021| Modified on May 28, 2023
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.

Related Links:

Melatonin for Stroke Recovery and Prevention
Stroke Recovery and Prevention Remedies
Top Natural Treatments for Heart Disease (Cardiovascular Disease)

Boost O2

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Posted by Shirley M. (Sedona) on 01/20/2021

This is a good reason for carrying a can of BOOST O2 in the car and have handy in the house until medical help arrives.

EC: Thank you so much, what a great idea. Added your idea to the supplements section in the CO article above.

Replied by Zal

I guess Hydrogen water is also worth having?

Colloidal silver?

Carbon Monoxide Poisoning Danger

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Posted by Michael (New Zealand) on 07/10/2022


This newspaper article draws attention to the danger of Carbon Monoxide poisoning in mountain huts, where climbers / trampers are naturally very keen to get warm, especially in the winter. Some go to sleep and never wake up!

Several people have unfortunately died from CO poisoning in alpine huts in New Zealand over the years! It is one of many aspects of Mountain Safety that people should acquaint themselves with prior to venturing out into the "Great Outdoors".

That stove in the corner of that welcoming hut is not always your friend!

Have I shocked you - I hope so!

I looked into my old tramping guide book from the 'seventies and could find no reference to CO poisoning in the index of an otherwise excellent book. The other knowledge contained therein must surely have saved my life on more than one occasion, that is the measure of the value of such knowledge.

The above tragedy happened to a guy who was probably well versed in the mountains, so it should serve as a cautionary tale to all those setting out for the first time into the Wilderness, as well as those of us who think they have "Read the Book"!!

Joining a tramping/skiing/climbing club is invaluable if you are prepared to listen to other more experienced members, who are usually very happy to share their experience and knowledge (O.K. even brag about it -still useful to know!). Clubs often organize safety courses of one sort or another too. Attend those courses and listen and learn. Leaders need to know all of this safety stuff especially well of course! Being a club member can be fun and enjoyable too!

CO is an insidious gas because it can sometimes go undetected !!!

Cheers from Down Under (Where the mountains are pretty cold right now!)

Carbon Monoxide Poisoning From Generators

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Posted by Deirdre (Earth Clinic) on 07/08/2022

This is a warning post to everyone who hasn't read my 2021 article on carbon monoxide poisoning to please be careful any time you use a generator, lawn mower, or basically any gasoline-powered engine. I am moving soon and was just outside the garage door selling a new gas and electric powered generator to someone. He turned it on to make sure it worked before carting it away and it spewed a TON of exhaust into the air when it kicked on. He kept it on no longer than about a minute. However, the exhaust/carbon monoxide went into the garage, and when I went upstairs into the kitchen a few minutes later, discovered the whole kitchen reeking of exhaust. When you smell gasoline exhaust, you are inhaling some level of carbon monoxide.

I took the dog for a walk and 20 minutes later the kitchen (!) still reeked of exhaust. That's when I pulled out my handy little carbon monoxide reader and found that carbon monoxide was spiked in the kitchen. Also in the garage, slightly more so.

Please remember that the smallest amount of carbon monoxide can cause brain and heart damage. I did a lot of research on this when I wrote the article and I feel very strongly it's the most underreported cause of heart attacks and strokes, despite being heavily studied in the auto industry for many decades.

I used an electric leaf blower to blast the carbon monoxide out of the garage and my meter went back to 0 quickly. (No, did not use the blower in my kitchen!) That is one of the fastest ways you can clear toxic gas. Opening the windows and doors takes a lot longer.


1 User Review
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Posted by Jill (Toronto) on 01/20/2021

1 teaspoon of cayenne powder in a small amount of juice or water for suspected CO poisoning. Don't forget to give it to your pets if you suspect they also got a nasty hit of carbon monoxide outside. I noticed one of my dogs sometimes gets agitated for no apparent reason after we come back from a long walk. Maybe that's the reason.

Methylene Blue

1 User Review
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Posted by Lisa (HI) on 01/19/2021

I use methylene blue to combat carbon monoxide (CO) and other oxidation issues. I use a drop of the aquarium solution, can mix in water or take straight. Too much ( like 60 drops of the 2% solution can be toxic ) based on weight (150lb person).

It is also good for parkinsons, alheizmers, old age dementa. etc. They are all oxidative damage. People with genetic disorders take it daily for their entire life without bad effect.

I have been taking it for about 8 years now daily. There is a genetic disorder that can affect (mostly asian people) and they can get anemia if they take it (in large doses) but that is very rare in others. It also helps with covid and certain parasites. Used for 60 years to treat malaria.

Oil Pulling

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Posted by Melissa (Kansas City, Mo) on 10/17/2016

Oil Pulling Cured Migraines From Carbon Monoxide Poisoning

I was in a carbon monoxide accident a few weeks ago. Although I was very lucky to survive, the migraines felt like a brain freeze that lasted hours of each day. I couldn't think or see straight. I avoided filling the prescription for pain pills from the doctors and was going to wait it out a month and see if I could find an alternative route. I did try aspirin, excedrin, ibuprofen, and Tylenol. Nothing helped the pain at all. I started oil pulling last Thursday night with organic sesame seed oil (medium heat) and I have not had a migraine since that day. I do it twice a day for 20 minutes. A place I spend extra time with the oil is under the tongue, but I also swish it all around. The world needs to know about this. I'm so grateful.

Preventing Carbon Monoxide Poisoning

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Posted by KT (Usa) on 11/19/2018

Dear EC, I wanted to post a warning to those who use wood stoves about the importance of using a Creosote Sweeping Log. I usually burn one about every couple of months and at the end of the season. Last year the weather got so nice so fast I failed to do that.

When we first started using the wood stove again I knew I needed to use the CSL early this year but I kept putting it off until I just forgot. Yesterday I started getting this headache and had a hard time keeping the fire going in the wood stove. It just never dawned on me about the chimney clogging and carbon monoxide until last night. Then I remembered I neglected the CSL.

I slept with my window cracked and and told my husband to do the same thing. This morning when I went downstairs the fire he had started was burning at a slow pace so I advised him to let it burn down to coals as I needed to burn the CSL and turned our thermostat back so it would stop circulating the toxic air. I cracked our kitchen window, which is on the second floor after I stood outside taking some deep breaths. It seems better in the house now but cold. We have some small heaters to use in each room.

We clean our stove every year and our chimney has a liner due to a previous chimney fire. Burning the CSL logs have worked fine every year since our fire. I just neglected to do that at the end of last season and wanted to give a "heads-up" about it.


Replied by Robert Henry
(Ten Mile, Tn)

KT,,,,,,, girl, you just sent me to school. I was not aware of a CSL log until your post. I am aware of creosote and how it can burn down your home. An ole timer said to burn potato peeling in your heater and that will keep it clean. Did not work for us, so we have it cleaned ever other year.

Normally, we just bang on the flue and the stuff falls and we clean that up. Over the years we always had a fireplace. The are only fit to look at. No heat like a heater. Our heater stands on a stone hearth that goes to the ceiling in the back. The heater has a glass front and a fan. The fire has to be small, least it run all out of the house. We get to see and feel the fire.

In the fall we go to the corn fields and pick up the left over corn cobs.... about a bushel. We keep a small pail of them soaking in diesel. When we want to build a fire we use one with a handful of kindling along with some very small logs and have an instant fire.

Waste not, want not. We take the dead ashes and spread them along the base of out house. Thus, we never have a need for an exterminator, no insects ..... Did I ever tell you that I was an eagle scout about 66 years ago.

Kt, if folks read the EC posts, their lives well so much better. Got some smart people here. Thank you for sending me to school.


Replied by KT

Dear ORH,

Small fires create a swirling effect and that's what can coat & clog the chimney. We were advised to initially burn our stove hot in the morning to burn out any coating. I just scanned, looking for your post about breathing...maybe your chimney is closing up and the shallow breathing could be a danger to you and your tractor driver.

I don't think using diesel soaked corn cobs is safe. I get "Starter Logg" and we also use "Strike-A-Fire". Even though cardboard is not the best, I save our toilet paper and paper towel rolls all year and use with newspapers and twigs/kindling from our yard to start fires.

I think it would be a good idea to get a couple CSL's and use one now to make sure you are not reducing your own oxygen supply in the house.


Replied by Robert Henry
(Ten Mile, Tn)

KT, think you are right about the small fires, but our family room is 22' high and the flue is close to that. Even a small fire will run us out of the house.

What I've learned is that safety is knowing how to handle something. I've handled lot of hazardous materials in my life and a soaked corn cob is not a problem. We used that trick most of our lives. I thank you for your concern however.

I am going to get some of those logs.


Strokes and Heart Attacks

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Posted by John (AU) on 01/20/2021

I know a few people who had heart attacks or strokes outside or within an hour of coming inside from a walk or run. Some elderly, some under the age of 50. One in particular worked on trailers and multiple heart attacks on the same day was young and in good health. He survived but had extensive heart damage after that and was never the same.

Replied by Mary

What about all of the thousands and thousands of people waiting in their cars to either get tested or get the covid 19 vaccine. Maybe this is why so many are being tested positive or once in the hospital are testing for all of the above???


Not to mention this new experimental medical shot has caused many to have heart conditions, there's many FB groups with people sharing their symptoms or losing family members. we should be able to talk about this! many deaths yet no one is discussing this.


And all the cars waiting in line at parent pick up at so many schools!