If the air is clean, you can't see, smell or taste it. It contains approximately 78 percent nitrogen gas (N 2 ), 21 percent oxygen gas (0 2 ). There is still one percent left.
This is made up of trace substances whose concentration can change: the noble gas argon (Ar), carbon dioxide (C0 2 ), hydrogen, water vapor and a touch of other gases.
Air is not a luxury!
Clean ones already. At least there is some good news first: the air has gotten better again in many European cities, although not yet good enough. If you live in a metropolis or on a busy street, you may turn your nose up at the outside air and prefer to keep your windows closed - but of course the air comes in from nowhere other than outside.
But that doesn't mean that it's the same inside as it is outside the door. And now comes the unpleasant news: Especially where most of us spend around 90 percent of our time - namely indoors - the air quality often leaves a lot to be desired.
Why does it smell bad here?
“There is a lack of oxygen,” many complain when rooms smell stale. And as a rule, they make a clear misdiagnosis: In a sealed room of around 20 m 2 , the existing O 2 can last for days. So it's not because there's too little oxygen if there's thick air in the office, classroom or living room; often not to colleagues, classmates or roommates - no, an excess of harmful substances usually takes our breath away.
What's going on in the room
Wherever people are, they breathe, work, cook, clean, sleep and perspire. And in doing so, they constantly release carbon dioxide into the air. If there is no ventilation, the CO 2 pollution increases significantly. Above all, however, the concentration of air pollutants increases in unventilated rooms, which can make you smelly, tired and sick. Measurements have shown that indoor air is up to eight times more polluted than outdoor air! Some harmful substances come into the indoor air through the outside air, but many come from materials that are in the room: We breathe in what household cleaners, paints, varnishes, adhesives, carpets and furniture emit - sometimes for years.
What's going on? Fine dust, carbon dioxide, nitrogen dioxide, VOC (Volatile Organic Compounds), allergens and mold spores.
Formaldehyde is a colorless gas that often stings your nose indoors: Elevated concentrations irritate the respiratory tract and the mucous membranes of the eyes and nose. Formaldehyde can escape from natural substances such as wood or fruit and is used as a chemical base in many products.
We constantly release carbon dioxide into the surrounding air when we breathe. C0 2 is a gas that is produced by the combustion of gasoline, coal, wood, gas, candles. You notice immediately when the concentration of carbon dioxide increases in a room: fresh air smells different!
Nitrogen dioxide is a highly irritating gas. High concentrations are measured in road traffic; diesel vehicles in particular emit a lot of N0 2 . Indoors, gas, wood and other fuels that burn in open fireplaces release nitrogen dioxide into the air - as do burning candles and cigarettes.
VOC is the abbreviation for Volatile Organic Compounds. They evaporate from liquid and solid materials or escape into the air as a gas at low (room) temperatures - and irritate the skin and nose. VOCs arise in nature (for example methane in swamps) and escape from all living things.
Countless products that we use in everyday life also secrete these substances: On the one hand, there are chain-shaped hydrocarbons - found, for example, as degreasers in household cleaning products - and on the other hand, there are ring-shaped hydrocarbons that outgas from paints and adhesives, for example.
VOCs include hydrocarbons, alcohols, aldehydes and organic acids, solvents such as benzene, toluene, xylene, liquid fuels and synthetic substances.
