Definition and principal sources

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that can be toxic to humans and animals. Carbon Monoxide is produced by devices that burn fuels (wood, oil or gas), this process is known as combustion which subsequently releases smoke including CO into the atmosphere. Boilers, room heaters, furnaces, charcoal grills, cooking ranges,water heaters, fire places and wood burning stoves are all sources of CO.

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Health Effects

The World Health Organization has identified a number of detrimental human health effects from CO exposure. These include:

  • Headaches, dizziness, disorientation, nausea, and fatigue when exposed to low concentrations
  • At low concentrations, fatigue in healthy people and chest pain in people with heart disease.
  • Impaired respiratory system activity, even in individuals without pre-existing respiratory issues occurs when exposed to moderate concentration.
  • At moderate concentrations, angina, impaired vision, and reduced brain function may result.
  • At higher concentrations, impaired vision and coordination; headaches; dizziness; confusion; nausea.
  • Death when exposed to high concentrations. Due to the formation of carboxyhemoglobin in the blood, which inhibits oxygen intake.


Malfunctioning appliances, as well as outdoor sources, can all increase indoor Carbon Monoxide levels beyond the recommended healthy levels. Regular checks of such appliances are recommended to guarantee that they are in the best possible working order to minimise the exposure of Carbon Monoxide in your environment. Regular checks combined with the implementation of an air purifier into any space will ensure the best possible standard of living.

WHO recommends that emission rates from indoor combustion do not exceed the below levels as a 24hour average to achieve minimal health risks (@):

Unvented : 0.16 (g/min) (i.e. without a chimney or hood)

Vented : 0.59 (g/min) (i.e. with a chimney or hood) (@)

For vented devices, an average of 25% of total emissions is assumed to enter the room.

Separate guidance is provided for unvented and vented stoves as those technologies with chimneys or other venting mechanisms can improve indoor air quality through moving a fraction of the pollutants outdoors (@). These emission rate targets will result in 90% of homes meeting WHO Air quality guideline values for CO as a 24-hour average.

Further Information

EPA – Steps to reduce exposure to Carbon Monoxide

Neuroscience and Biobehavioral reviews – Carbon Monoxide and the nervous system

Consumer Product and Safety Commission US – Carbon Monoxide questions and answers


What’s in the Air

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