Carbon Dioxide: Health And Safety Hazards Fact Sheet

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Carbon dioxide in a sealed structure, such as a refuge station, safe haven or controlled environment, can quickly build up and damage your...
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Carbon dioxide (CO2) naturally occurs when you exhale. However, when in a sealed structure, such as a refuge station, safe haven or controlled environment, it can quickly build up and cause significant damage to your health.  Knowing the health and safety hazards of CO2 is necessary when dealing with refuge chambers and safety protocols.

What is Carbon Dioxide?

CAS Number: 124-38-9

Chemical Compound: CO2

Other names: carbonic anhydride, Dry ice, carbonic acid gas

Chemical Properties

Molecular weight:                144.009 g/mol

Boiling point:                        -78.48°C

Melting point:                       -10°C

Vapour pressure:                   56.5 atm

Relative gas density:             1.53

Carbon dioxide (CO2) is a colourless and odourless gas existing in Earth’s atmosphere as a trace gas at a concentration of about 400ppm (0.04%) by volume. Natural sources of CO2 include volcanoes and hot springs, and being soluble in water, it occurs naturally in groundwater, rivers, lakes, ice caps, glaciers, and seawater. It is also present in deposits of petroleum and natural gas.

Carbon dioxide is produced by all aerobic organisms when they metabolise carbohydrate and lipids to produce energy by respiration — expelled to the air via the lungs of air-breathing land animals, including humans. It is also produced during the decay of organic materials and by the combustion of wood, carbohydrates and fossil fuels such as coal, peat, petroleum and natural gas.

How Carbon Dioxide is Used

Carbon dioxide occurs naturally in the environment and is a commonly used chemical. Applications of its use range from consumer-related (food and beverage additive, de-caffeinate, or refrigerant), safety (fire extinguisher), manufacturing (pneumatic systems, chemical processing, or production of plastics), oil recovery, and pharmaceutical (as a solvent).  

Safety Hazards of Carbon Dioxide

Although carbon dioxide is technically not classified as toxic or harmful, it can be fatal in high concentrations. 

CO vs. CO2

Carbon Monoxide and Carbon Dioxide are often mistaken for one another. Because 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 Dioxide Levels

Carbon Dioxide can be measured using a non-dispersive infrared (NDIR) sensor. Measurement is based on the physical property that CO2 molecules absorb infrared light or particular wavelengths. By shining light through the target gas and using suitable optical filters, the light detector will give an output that can be converted into a CO2 concentration value.

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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