When the air is pure, you don't see, smell, or taste it. It contains about 78 percent nitrogen gas (N2), 21 percent oxygen gas (02). That leaves one percent remaining.
This consists of trace substances whose concentration can vary: the noble gas argon (Ar), carbon dioxide (C02), hydrogen, water vapor, and a hint of other gases.
Air is not a luxury!
Clean air is. At least there's some good news upfront: In many European cities, the air has improved again, though not yet good enough. Those living in a metropolis or on a busy street may wrinkle their noses at the outdoor air and prefer to keep their windows closed - but of course, the air comes from nowhere else but outside.
But that doesn't mean the air inside is the same as outside. And now comes the unpleasant news: Especially where most of us spend about 90 percent of our time - indoors - the air quality often leaves much to be desired.
Why does it smell musty here?
"It's lacking oxygen," many complain when rooms smell stale. And they usually make a clear misdiagnosis: In a sealed room of about 20 m2, the available O2 lasts for days. So it's not due to too little oxygen when the air is stuffy in the office, classroom, or living room; often it's not because of colleagues, classmates, or roommates - no, an excess of harmful substances usually takes our breath away.
What is bustling around in the room
Where people stay, they breathe, work, cook, clean, sleep, and sweat. And in doing so, they constantly release carbon dioxide into the air. If not ventilated, the CO2 load increases significantly. Above all, in unventilated rooms, the concentration of air pollutants that can smell bad, cause tiredness, and make you sick rises. Measurements have shown that indoor air is up to eight times more polluted than outdoor air! Harmful substances partly come from outside air into indoor air, but many originate from materials present in the room: we inhale what household cleaners, paints, varnishes, adhesives, carpets, and furniture off-gas – sometimes for years.
What all flies around? Fine dust, carbon dioxide, nitrogen dioxide, VOCs (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 materials like wood or fruit and is used as a chemical base in many products.
Carbon dioxide is constantly released into the surrounding air when we breathe. CO2 is a gas produced by the combustion of gasoline, coal, wood, gas, and candles. You immediately notice 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, especially diesel vehicles emit a lot of NO2. Indoors, gas, wood, and other fuels burning in open fireplaces release nitrogen dioxide into the indoor air – as do burning candles and cigarettes.
VOC is the abbreviation for Volatile Organic Compounds, that is, volatile organic compounds. They evaporate from liquid and solid materials or escape as gas at low (room) temperature into the air – irritating skin and nose. VOCs occur naturally (for example, methane in swamps) and are emitted by all living beings.
Countless products we use daily also emit these substances: on the one hand, chain-shaped hydrocarbons – found, for example, as grease removers in household cleaners – and on the other hand, ring-shaped hydrocarbons that off-gas from paints and adhesives.
VOCs include hydrocarbons, alcohols, aldehydes, and organic acids, solvents such as benzene, toluene, xylene, liquid fuels, and synthetic substances.
The author: Peer-Arne Böttcher
Peer is the founder of AIRY and passionate about the topic of healthy indoor air. For many years, he has been intensively engaged with the scientific foundations and technical possibilities of how our breathing air can be sustainably improved – completely without chemicals, filters, or electricity.
