Carbon Monoxide: Health And Safety Hazards Fact Sheet

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Carbon monoxide in a sealed structure, such as a refuge chamber or safe haven, can quickly build to toxic levels - learn about the dangers...
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Carbon monoxide (CO) is one of the most commonly know dangerous gases. Often a by-product of chemical reactions, it also naturally occurs when you exhale.

Within a sealed structure, such as a refuge chamber, safe haven or controlled environment, it can easily build up and cause significant damage to your health.  Knowing the health and safety hazards of CO is necessary when dealing with refuge bay safety protocols.

What is Carbon Monoxide?

CAS Number: 630-08-0

Chemical Compound: CO

Other names: carbon monoxide, Carbonic oxide, carbon(II) oxide, exhaust gas, flue gas

Chemical Properties

Molecular weight:                28.01 g/mol

Boiling point:                        -191.5°C

Melting point:                       -205.02°C

Vapour pressure:                  >35 atm

Relative gas density:             0.97

Carbon monoxide (CO) is a colourless, odourless, and tasteless gas that is slightly less dense than air. It is highly toxic to haemoglobin animals (including humans) when encountered in concentrations above 35ppm.

In the atmosphere, CO is produced from incomplete combustion and is present in exhaust gasses of vehicles and other engines, and from the burning of most fuels. It is also produced in low quantities in normal animal / human metabolic processes and human blood at levels of between 0 and 3% for healthy adults. This level is higher in heavy smokers.

How Carbon Monoxide is Used

Carbon monoxide is a commonly used industrial chemical. When formed as a producer or water gas, applications of its use range from fuel in industrial operations to a reducing agent.  

Safety Hazards of Carbon Monoxide

Carbon monoxide is extremely dangerous to humans and other biological life forms. Due to its nature, even low concentration can have a severe impact. 

CO vs. CO2

Carbon Monoxide and Carbon Dioxide are often mistaken for one another. Often, both gases are odourless, colourless, target the cardiovascular system, and enter the body through inhalation, skin, or eyes. They also possess similar symptoms if affected, such as headaches, dizziness, seizures, and hallucination.

However, the two gases have very different properties and safety protocols. Below is a summary list of the differences between the two gases.


Carbon MonoxideCarbon Dioxide
Doesn’t occur naturally in the atmosphereOccurs in the natural atmosphere
Result of oxygen-starved combustion in improperly ventilated fuel-burned equipmentA natural by-product of human and animal
respiration, fermentation, chemical reactions, and combustion fossil fuels/woods
Generated by any gasoline engine WITHOUT a catalytic converterGenerated by any gasoline engine WITH a catalytic converter
A common type of fatal poisoningPoisoning is rare
Flammable gasNon-flammable gas
Symptoms: confusion, nausea, lassitude, syncope, cyanosis, chest pain, abdominal painSymptoms: dyspnoea, sweating, increased heart rate, frostbite, convulsion, panic, memory problems
Target organ: lungs, blood, central nervous systemTarget organ: respiratory system
Based on the Occupational Safety & Health Administration (OSHA) standards, the permissible exposure limit (PEL) is 50 parts per million (ppm)Based on the OSHA standards, the PEL is
5,000 ppm
Based on the National Institute for Occupational Safety and Health (NIOSH) standards, the recommended exposure limit (REL) is 35 ppmBased on the NIOSH standards, the REL is 5,000 ppm

How to Monitor Carbon Monoxide Levels

Carbon Monoxide is detected using an electrochemical gas sensor that measures CO concentration by oxidising it at an electrode and then measuring the resulting current. To reduce cross-sensitivity to other combustible gases, it has chemical filters for H2S, N02, NO and SO2.

Measuring CO levels aids in the detection of fires and heating underground. Sensors will detect a steady increase in concentrations of CO without reduction. Although shot firing fumes and diesel exhaust can trigger carbon monoxide alarms, rapid increase and decrease patterns are known.

Removing Carbon Monoxide in a Refuge Chamber

As the name suggests, chemical scrubbers remove ‘scrub’ the air using a chemical to remove harmful gases. Refuge chambers use dry chemical scrubbers to remove CO and CO2 from the internal environment, especially if compressed air fails or becomes compromised.

Providing breathable air within a refuge chamber is a challenge, along with disposing of the carbon dioxide and carbon monoxide we breathe. As occupants within the sealed environments breathe, CO2 and CO will build up. If these gases are not removed from the internal atmosphere, they can build to toxic levels and poison the chambers inhabitants.

Numerous gases associated with mining, tunnelling and underground construction are generalised into combustible, toxic and asphyxiate types. Because of the hazardous nature of these gases and the unique and restrictive structure of underground environments, these gases must be continuously monitored to mitigate risk.

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