Carbon Dioxide (CO₂)

Description of carbon dioxide:

Carbon dioxide is odorless at low concentrations. At high concentrations, the climate gas gives off a sharp to sour odor - this is also perceptible to humans. CO₂ is, for example, heavier than oxygen and collects at ground level and in depressions.

Over the course of Earth's history, the proportion of carbon dioxide in the Earth's atmosphere fluctuated greatly. The first measured carbon dioxide values from 500 million years ago indicate a CO₂ content of approximately 8,000 ppm (parts per million). For a variety of chemical, biological and physical reasons, this proportion continuously decreased to under 2,000 ppm. For at least 800,000 years, the carbon dioxide concentration has always been below 300 ppm. In particular through industrialization and the associated burning of fossil fuels, the CO₂ proportion rose again for the first time to today's value of up to 415 ppm.

Limit values for carbon dioxide:

The proportion of carbon dioxide in the air we breathe today is approximately 415 ppm (equivalent to 0.04% of the air). The exhaled air of a human has a CO₂ content of approximately 40,000 ppm. Accordingly, concentrations of up to 5,000 ppm can quickly be measured in unventilated bedrooms and fully occupied classrooms or meeting rooms.

And these high carbon dioxide concentrations are harmful to concentration, performance and health in general.

The German Federal Environment Agency (UBA) therefore recommends letting fresh air into the room from outside as soon as a value of 1,000 ppm CO₂ is exceeded. The so-called maximum workplace concentration, also known for short as the MAK value, is given as 9,100 mg/m³ (equivalent to just under 5,000 ppm). The now no longer valid DIN 1946-2 provided for a limit value of 1,500 ppm. 

Effects of excessive CO₂ concentration:

CO₂ concentrations of over 1,000 ppm have been proven to result in more mistakes at work. This can happen, for example, through lack of concentration or headaches when doing calculations, with spelling, or when finding spelling errors while proofreading.

If the proportion of carbon dioxide rises to 2,000 ppm, lapses in concentration and fatigue can be observed. From 5,000 ppm, a marked decline in performance and the onset of headaches can even be expected.

The problem with this: symptoms such as lapses in concentration or headaches occur long before the indoor air is consciously perceived as bad.

As the CO₂ content rises, minute ventilation increases continuously and can even become life-threatening. A carbon dioxide concentration of approximately 80,000 ppm leads to shortness of breath and, after 30 to 60 minutes, to death.

Formation of carbon dioxide

Carbon dioxide is formed during the complete combustion of carbon-containing substances such as plant residues and oil, for example in the form of fuel, as well as in the organism of living beings as a product of cellular respiration. During incomplete combustion, on the other hand, carbon monoxide is formed.

Indoors, besides breathing people and any animals present, combustion processes (gas stoves, oil/wood/coal/gas ovens, candles, tobacco products etc.) are above all sources of large amounts of CO₂. These are typically gas stoves, candles, cigarettes and cigars, or stoves that burn oil, wood, coal or gas. CO₂ is likewise released to a smaller extent by carbonated beverages.

Sensor used:

Carbon dioxide is measured by means of an optical sensor. This is based on the principle of infrared absorption. The CO₂ molecule absorbs certain wavelengths of infrared radiation. This is, for example, also the reason for the greenhouse effect, since this heat radiation cannot leave the Earth. The sensor measures how high this is. To achieve maximum accuracy, the intensity of the infrared LED is additionally monitored with a second measuring beam. The advantage of this principle over single-beam measuring methods is high accuracy. There are no disadvantages. The sensor we use has no known cross-sensitivities to other gases.

Measuring carbon dioxide:

Measure carbon dioxide as well as pollutants in the indoor air of an office or home in real time - with the air-⁠Q air analyzer, which can be ordered here.