Critical Environment Technologies Canada Inc. (CETCI)

Carbon Monoxide (CO) Versus Carbon Dioxide (CO2)


Carbon monoxide (CO) and carbon dioxide (CO2) are often mistaken for one another. Both gases are odourless and colorless and target the cardiovascular system. Both gases can enter the body through inhalation, skin and / or eye. Similar symptoms that both gases have in common are headaches, dizziness, seizures, and hallucination.

Most people have a hard time determining the difference and do not realize that vehicle exhaust emits both CO and CO2. In an indoor environment, this build-up of gas can be hazardous to the health and safety of the individual exposed to it.

CO has been referred to as the “Silent Killer” (The Dangers of Carbon Monoxide). Once CO is inhaled, oxygen levels are displaced in the blood causing vital organs to starve. Therefore, causing people to suffocate and lose consciousness.

CO2, on the other hand, is referred to as “hypercarbia or hypercapnia” (Carbon Dioxide Poisoning). Since our blood expels CO2, inhaling more CO2 would cause the inability for the body to expel the gas.

Additional differences in CO and CO2 are addressed in the table below:

Carbon Monoxide

Carbon Dioxide

Doesn’t occur naturally in the atmosphere


Result of oxygen starved combustion in improperly ventilated fuel-burned equipment



Generated by any gasoline engine WITHOUT a catalytic converter


Common type of fatal poisoning


Flammable gas


Symptoms: confusion, nausea, lassitude, syncope, cyanosis, chest pain, abdominal pain



Target organ: lungs, blood, central nervous system


Based on the Occupational Safety & Health Administration (OSHA) standards, the permissible exposure limit (PEL) is 50 parts per million (ppm).

Based on the National Institute for Occupational Safety and Health (NIOSH) standards, the recommended exposure limit (REL) is 35 ppm.

 Occurs naturally in the atmosphere


Natural by product of human and animal respiration, fermentation, chemical reactions, and combustion fossil fuels/woods


Generated by any gasoline engine WITH a catalytic converter 


Poisoning is rare


Non-flammable gas


Symptoms: dyspnea, sweating, increased heart rate, frostbite, convulsion, panic, memory problems


Target organ: respiratory system


Based on the OSHA standards, the PEL is 5,000 ppm.



Based on the NIOSH standards, the REL is 5,000 ppm

 NOTE: Sources for the table above are referenced from, and NIOSH Pocket Guide to Chemical Hazards.

Since it is extremely difficult to detect CO and CO2 gases based on the symptoms alone, installing a gas detector is suggested. There are a large range of detectors available on the market; therefore, choosing the right one that suites your need is ideal. Choose a gas detector from a manufacturer that is reputable and has their products tested by certain standards such as the Canadian Standards Association (CSA), Underwriters Laboratories (UL), etc.

For suggestions on a fixed gas detection system, please visit




Bose, Debopriya. “Carbon Dioxide Poisoning.” 26 December 2011. Web. 31 May 2012. .

Bose, Debopriya. “Carbon Monoxide Poisoning: Causes, Symptoms and Treatment.” 2011. Web. 31 May 2012. .

“CO and CO2 – What’s the difference?” 27 August 2009. Web. 31 May 2012. .

“Dangers of CO2: What You Need to Know.” 25 October 2011. Web. 31 May 2012. .

“The Danger of Carbon Monoxide.” Silent Shadow: Silent Killer. 2004. Web. 31 May 2012. .

“Exposure to CO2 Leads to Fear of Suffocation.” 12 January 2010. Web. 31 May 2012. .

“NIOSH Pocket Guide to Chemical Hazards.” Centers for Disease Control and Prevention. 04 April 2011. Web. 01 June 2012. .

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