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Indoor Air Pollution

According to the French indoor air quality monitoring centre (OQAI), on average we spend more than 80% of our time in enclosed spaces, whether at home, work or school. Although pollution is usually associated with the outdoor environment, this is simply because we notice it more: the smell of exhaust fumes, various other types of fumes, etc.

However, the air we breathe indoors also contains pollutants and various potentially toxic products. According to the US Environmental Protection Agency, indoor air is up to 5 times more polluted than outdoor air! So what are these chemical substances present in our homes, what are their effects and how can we protect ourselves from them?

What does indoor air quality refer to?

Although in theory the air we breathe is mainly made up of nitrogen and oxygen, in actual fact it contains multiple substances in varying amounts. Some of these substances are harmless while others are toxic at different doses.

Indoor air pollution partially comes from the external environment (transport, industry, etc.), but also from the home itself. Many pollutants are released into the air by the construction materials, coverings and paints in our homes, or by volatile particles present in domestic furniture and objects. There's also the chemical products we use for cleaning, steam from the kitchen and bathroom, fumes emitted by heating appliances, residue given off by the use of candles or incense, mould that can grow in the presence of humidity and dust mites in carpets, mats and mattresses. Lastly, the air we breathe in the home contains carbon dioxide, which is naturally produced by human activities, particularly from the breath of the people in a room.

All of these products, particles and pollutants gradually build up and adversely affect indoor air quality. In an attempt to limit energy losses in homes, insulation is often fitted at the expense of good ventilation, which gradually saturates the ambient air. This is a particular problem in very busy spaces (companies, administrative offices, etc.) and in buildings frequented by vulnerable individuals and children (creches, schools, etc.), where the confinement can quickly reduce the air quality.

Which pollutants are present in indoor air?

There are two categories of air pollutants in the environment: primary pollutants directly caused by pollution (nitrogen oxide given off by vehicles, sulphur dioxide released during the burning of fossil fuels, etc.) and secondary pollutants, which come from the chemical reaction of these primary pollutants with their environment (with UV light, the oxygen present in the air, etc.).
Indoors there are three main families of pollutant products:
  • Volatile organic compounds (VOCs)
Most volatile organic compounds are emitted by exhaust fumes, although they're also found in many domestic products and coverings: solvents, wood, adhesives and paint. They are released into the indoor environment, sometimes over a period of years, and compromise the air quality in a home. Volatile organic compounds include polycyclic and monocyclic hydrocarbons and aldehydes such as formaldehyde, which is particularly toxic.
  • Microparticles (MP)
Microparticles are very small pollutants suspended in the air. They are mostly released by heating, road traffic and industry. Although some are visible, most are miniscule, invisible to the naked eye and therefore particularly dangerous.
  • Carbon dioxide (CO2 )
Also known as carbonic gas, carbon dioxide is naturally present in the air and isn't toxic per se. Nevertheless, a high concentration in the home can have adverse health effects. The presence of carbon dioxide in the home may be due to external pollution, although its main source is the occupants, who release carbon dioxide when they breathe.

Indoor air can also contain various other toxic chemical substances such as heavy metals (lead, mercury, cadmium, etc.), combustion residues such as nitrogen oxide, sulphur dioxide and carbon monoxide, as well as ozone. Discover all our products

What is the health impact of bad indoor air quality?

Not all of the substances present in indoor air have a direct impact on the health of a home's occupants; some are even harmless or, like ethanol, present in tiny quantities. However, other particles pose a threat over varying periods of time and to varying degrees of toxicity depending on their concentration and the length of exposure.

Some volatile organic compounds are considered highly dangerous: this is the case with benzene and formaldehyde, which irritate the airways and are carcinogenic. This is why strict regulation governs the products responsible for the release of these VOCs. Microparticles are also potentially hazardous to health, particularly due to their small size, meaning they can enter deep inside the respiratory system. Heavy metals also pose a threat: although present in small quantities, they can nevertheless build up in the body over time.

Carbon dioxide is a slightly different case and is only toxic at high doses. The normal amount of CO2 in the air is around 400 ppm (parts per million) and health effects are only observed above 1,000 ppm: headaches, drowsiness, a decline in intellectual and psychomotor performances, etc. At very high doses, carbon dioxide can even be fatal if the concentration in the indoor air exceeds 25%.

Most of the pollutants present in indoor air irritate the respiratory system, the eyes and the mucus. This is the case with ozone, nitrogen dioxide and sulphur dioxide. However, the most toxic product in the short term is carbon monoxide. This invisible and odourless gas can spread in the home due to a defective heating system and can be fatal for a home's occupants.

How to measure indoor air quality

Various tools are available for measuring indoor air quality. CO2 sensors measure carbon dioxide concentration using an infrared detection system. There are devices for detecting COVs in indoor air, with the most sophisticated even giving a measurement for each gas present and indicating the level of the most toxic substances, namely formaldehyde and benzene. Also available are fine particle sensors, which work using a photodetector.

Solutions for combating poor indoor air quality

Solutions are available for preserving indoor air quality and limiting pollution in enclosed spaces. Regulations are in place to monitor indoor air quality in schools (decree no. 2015-1000 of 17 August 2015), exposure thresholds have been set for the workplace and labelling is used to identify items responsible for emitting COVs so that consumers can choose products that pose a lower health risk.

As a general rule, it's best to buy domestic products (furniture, decorative items, coverings and cleaning products) that are ecological and do not pose a risk of toxicity. Next, remember to have your boiler regularly serviced to prevent the risk of carbon monoxide poisoning. Detectors that identify this poisonous gas are also available.

It's also a good idea to have depolluting indoor plants in your home, which absorb pollution and in particular COVs. Although scientists question how effective this plant-based purification is, and plants are not enough to completely eliminate pollution from the home, it's worth doing this to improve the ambient air quality.

However, the most important thing for improving indoor air quality is proper ventilation. Fitting an effective ventilation system, not closing any ventilation in the home in an attempt to save energy and ventilating the living areas every day are the basics of good indoor air quality. Taking these steps refreshes the air in your home, cuts the concentration of gases and particles and gets rid of excess humidity, which is also responsible for respiratory problems and mould.

Devices such as the Netatmo Healthy Home Coach can be a help: this regularly assesses the indoor temperature, humidity and air quality by measuring CO2 and tells you when it's time to ventilate a room.

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