The air we breathe everyday contains CO2. Naturally present in the atmosphere, CO2 only poses a problem if present at excessive levels in our environment. But where exactly does it come from and in what way is it a pollutant? Knowing more about it provides some of the keys to restricting its production in the atmosphere and its concentration in domestic indoor air.

What is CO2?

The air we breathe is mainly made up of nitrogen (78%) and oxygen (21%), as well as numerous pollutants (microparticles, VOCs, etc.) and gases in various proportions. These include CO2, the name of which comes from the formula for carbon dioxide, also known as carbonic gas. This colourless, odourless and inert gas is not toxic and is harmless in normal concentrations.

Comprised of one carbon atom and two oxygen atoms, CO2 is naturally present in the air and is a normal component of gaseous exchanges in the human body: the body captures oxygen via the lungs, which when we breathe out emit the carbon dioxide produced by our organs.

How is carbon dioxide formed?

Carbon dioxide is naturally produced by the process of respiration in the human body, as well as by all living organisms: animals as well as plants, through photosynthesis or the process of decomposition. Many human activities also create carbon dioxide emissions. This is particularly true of combustion activities linked to heating, industrial production, vehicles that use petroleum derivatives as a fuel and large-scale deforestation.

Industrialised countries' lifestyles and production activities are responsible for huge emissions of carbon dioxide. These emissions combine with the normal and natural production of gas, as well as with the forest fires and volcanic eruptions that regularly occur worldwide. It is estimated that 35 billion tonnes of carbon dioxide are released into the atmosphere every year as a result of human activities. The activity that generates the most CO2 is the burning of oil, followed by the burning of coal.
In a building, carbon dioxide can of course come from the outside and the pollution emitted by vehicles and surrounding businesses. However, the CO2 we can measure indoors comes more generally from people simply being present and the breathing of individuals in an enclosed space. In this case, an excessive concentration of people and insufficient ventilation of a space causes confinement and an excessive level of carbon dioxide. Discover all our products

What are the dangers of CO2?

CO2 is naturally present in the atmosphere and is not toxic. However, excessive levels can have serious consequences, both for the environment and our health.
  • CO2: the greenhouse effect and climate change
Carbon dioxide is the main greenhouse gas naturally occurring in the atmosphere. This greenhouse effect is perfectly normal and ensures that the temperature on Earth is sufficient to sustain life. However, if emissions of CO2 and other greenhouse gases become too high, that heat becomes trapped and the temperature rises. This is referred to as climate change. Rising emissions therefore pose a threat to the environment, and more than 1 million kg of CO2 is emitted every second worldwide, due in large part to the use of fossil fuels (oil, natural gas and coal).
Climate change is responsible for phenomena including the melting of the polar ice caps, rising sea levels and accelerated desertification, which are serious issues for the future of the planet and many species. In addition to climate change, greenhouse gases are also responsible for mutations in plants and the acidification of the water in our oceans.
  • CO2 and health
Carbon dioxide is non-toxic and is not considered a pollutant under French law. However, high levels in the atmosphere do have consequences. In 2016, this concentration reached a record level of 403 ppm (parts per million), the highest level ever measured. According to the IEA (International Energy Agency), CO2 levels have risen by 120 ppm since the start of the industrial era.

Exposure to CO2 at high doses over an extended period can be harmful if the concentration in the air exceeds 10% or even fatal if it exceeds 20%. Although the levels measured in the environment are nowhere near this high, we know that a rise in CO2 in the air changes our respiratory flow and can cause asthma and breathing problems.
  • CO2 and indoor air quality
Although exposure to CO2 outdoors is not usually life-threatening, levels need to be very closely monitored in enclosed spaces. According to the French indoor air quality monitoring centre (OQAI), indoor air can be up to 5 times more polluted than outdoor air. In very busy and poorly ventilated spaces (homes, schools or businesses), the limit values can be quickly reached.

The normal level is 400 ppm in the air. Above 1000 ppm, air quality falls and you may experience headaches, vertigo, eye irritation and mucus, as well as attention problems.

CO2 is also a good indicator of confinement and air quality. If air isn't replaced sufficiently, there is a rise not only in the concentration of CO2 but also other pollutants (VOCs, fine particles, etc.).

How can you combat excess CO2 levels?

The authorities and scientists around the world are searching for solutions to restrict greenhouse gas emissions into the atmosphere. Several avenues can be developed:
  • Using non-CO2 emitting energy
Businesses and the general public can try to use more electrical energy and in particular renewable energy sources: hydraulic power, wind power, solar photovoltaic electricity, geothermal energy, etc. Indeed, 60% of the world's greenhouse gas emissions are caused by burning fossil fuels.
  • Cutting CO2 emissions
Cutting greenhouse gas emissions first of all requires more energy-efficient buildings. In France for example, tax credits have been introduced to encourage the installation of insulation and energy-efficient heating systems. Another key tool in cutting gas emissions is to restrict polluting vehicles and promote public transport. Lastly, new equipment and processes can also help to save energy in industry.
  • Capturing and storing CO2
To combat climate change, scientists have begun researching solutions that could allow us to capture the CO2 emitted and store it, notably in underground facilities. In the meantime, we already know that reforestation can capture some of the CO2 emitted and limit the damage that the greenhouse effect causes to the environment.

Limiting CO2 indoors

To ensure good indoor air quality and combat excess CO2 levels in the home, good ventilation is essential. Remember to regularly ventilate your home to refresh the ambient air. If you think you might forget, there are devices such as the Healthy Home Coach from Netatmo that measure CO2 levels in indoor air and notify you when it's time to ventilate a room.

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