Carbon monoxide is used as a chemical intermediate in some chemical processes (production of formaldehyde and methanol).
Substance name: Carbon monoxide
CASR number: 630-08-0
Molecular formula: CO
Synonyms: carbon oxide, carbonic oxide
Carbon monoxide is a highly poisonous, colourless, odourless and tasteless gas. It is very flammable and mixes well with air, easily forming explosive mixtures.
Melting Point: -205°C
Boiling Point: -191°C
Vapour density: 0.967 (air=1)(at 25°C)
Carbon monoxide will form when carbon in fuels (petrol, wood, coal, natural gas) is not burned completely. It is highly flammable.
Carbon monoxide is soluble in some organic solvents, such as ethyl acetate, chloroform and acetic acid. It will form toxic and flammable compounds when exposed to finely dispersed metal powders. It may react vigorously with oxygen, acetylene, chlorine, fluorine and nitrous oxide.
The National Pollutant Inventory (NPI) holds data for all sources of carbon monoxide emissions in Australia.
Levels normally present in the atmosphere are unlikely to cause ill effects.
Inhalation of low levels of carbon monoxide (200 parts per million for 2-3 hours) can cause headache, dizziness, light-headedness and fatigue. Exposure to higher concentrations (400 parts per million) of carbon monoxide can cause sleepiness, hallucinations, convulsions, collapse, loss of consciousness and death. It can also cause personality and memory changes, mental confusion and loss of vision.
Extremely high exposures to carbon monoxide can cause the formation of carboxyhaemoglobin and decrease the bodyâ€™s ability to carry oxygen. This can cause a bright red colour to the skin and mucous membranes causing trouble breathing, collapse, convulsions, coma and death.
Long term (chronic) health effects can occur from exposure to low levels of carbon monoxide. These effects may produce heart disease and damage to the nervous system. Exposure of pregnant women to carbon monoxide may result in low birth weights and other defects in the offspring.
Entering the body
Carbon monoxide can enter the body by inhaling contaminated air. When in the body, carbon monoxide is rapidly absorbed into the bloodstream from the lungs.
Most exposure occurs in the home. People can be exposed to carbon monoxide by smoking, using malfunctioning equipment (gas water heaters, fuel fired heaters, fireplaces and wood stoves, gas stoves, gas dryers), charcoal grills and using poorly vented automobiles. Workers in the industries that use or produce carbon monoxide are also at risk of exposure.
Workplace exposure standards
Safe Work Australia sets the workplace exposure standard for carbon monoxide through the workplace exposure standards for airborne contaminants:
- Maximum eight hour time weighted average (TWA): 30 parts per million (34 mg/m3)
These standards are only appropriate for use in workplaces and are not limited to any specific industry or operation. Make sure you understand how to interpret the standards before you use them.
Drinking water guidelines
There is no guideline for carbon monoxide in the Australian Drinking Water Guidelines.
Carbon monoxide can affect the amount of other greenhouse gases, which are linked to climate change.
Very high levels of carbon monoxide will cause the same problems for birds and animals that are experienced by humans, although these levels are unlikely to be experienced in the environment, except in extreme events such as bushfires. At high levels carbon monoxide will cause illness (fatigue, gastric upset) to animals.
At very high levels carbon monoxide will be life threatening. Long term (chronic) exposure to low levels of carbon monoxide may produce heart disease and damage to the nervous system.
As with women, exposure of pregnant animals to carbon monoxide may cause low birth-rates and nervous system damage to offspring.
Entering the environment
Industrial and diffuse (e.g. motor vehicles) emissions of carbon monoxide can produce elevated, but still low concentrations in the atmosphere around the source.
Volcanic eruptions, while sporadic, are significant contributors of carbon monoxide in their local area. Fires of all types will also contribute to carbon monoxide in the atmosphere.
Where it ends up
Carbon monoxide is usually emitted to the atmosphere.
Carbon monoxide affects the concentrations of methane (a greenhouse gas) and ozone in the atmosphere.
The National Environment Protection Council (NEPC) has established an ambient air quality standard (outdoor air only) for carbon monoxide. Currently the level is 9 parts per million of carbon monoxide averaged over an 8-hour period, with an allowable exceedence of once a year.
Industrial plants exhaust carbon monoxide to air from the combustion of natural gas, coal or coke. Examples of industrial plants that produce carbon monoxide include: metals (iron, steel, non-ferrous) manufacturing, electricity supply, mining (metal ore, coal), food manufacturing, oil and gas extraction, chemical manufacturing, cement lime, plaster and concrete manufacturing and petroleum refining.
Diffuse sources, and industry sources included in diffuse emissions data
Vehicles (including cars, trucks, aeroplanes, commercial shipping or boating, recreational boating, construction equipment, lawnmowers), fuel burning (for heating in the home, barbeques, bushfires) and cigarettes are thought to be some of the highest sources of diffuse emissions of carbon monoxide.
Carbon monoxide is emitted from volcanoes, marsh gases, natural gases in coal mines, forest fires, and can be produced from lightning. Some marine algae or kelp will produce carbon monoxide, as do some seed germinating processes.
Vehicle exhaust is the single biggest source of carbon monoxide.
No consumer products contain carbon monoxide, however many products will emit carbon monoxide when burned or operated. Such products include: automobiles (exhaust), tobacco (smoke), internal combustion engines (chainsaws, lawnmowers, leaf blowers etc.), non-electric heaters, charcoal grills and woodstoves.
Sources used in preparing this information
- Intergovernmental Panel on Climate Change (2001), Climate Change: Working Group 1: The Scientific Basis (Chapter 4), accessed May 2007.
- Merck and Co. 2001, Merck Index, 13th Edition, USA.
- National Environmental Protection Council, Ambient Air Quality NEPM, accessed May 2007.
- National Pollutant Inventory (1999), Contextual Information.
- New Jersey Department of Health and Senior Services, Hazardous Substance Fact Sheet: Carbon Monoxide, accessed May 2007.
- Office of the Australian Safety and Compensation Council, Exposure Standards: Carbon monoxide, accessed May 2007.
- Technical Advisory Panel 1999, Final Report to the National Environment Protection Council.
- United Nations, International Chemical Safety Cards: Carbon Monoxide, accessed May 2007.
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed June 2021.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018