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Measure CO2 levels reliably with CO2 sensors

When lots of people share a room, the air can get stale. This is mostly caused by exhaled carbon dioxide (CO₂). The results are: Reduction in well-being, concentration and performance.
Theben CO₂ sensors monitor CO₂ levels in schools and classrooms, in offices and meeting rooms or in passive and low-energy buildings. CO₂ sensors thereby make a decisive contribution to indoor air quality.
This site contains comprehensive information on CO₂ levels in indoor air and their effects as well as needs-driven and energy-efficient ventilation control using CO₂ sensors.

Background: Increased CO₂ levels and their consequences

We all know about badly ventilated houses, stuffy classrooms and meeting rooms. In addition to humidity and temperature, this is mainly due to exhaled carbon dioxide. An odourless and tasteless gas that is only detected by human beings due to its negative characteristics: feeling unwell, lack of concentration and deterioration in performance.

Human beings absorb oxygen from the air when they inhale and release carbon dioxide into the air when they exhale. Inhaled air contains 21% oxygen and 0.035% carbon dioxide. In contrast, exhaled air contains just 16% oxygen and 4% carbon dioxide. While carbon dioxide is only harmful to human beings at concentrations of 2.5% and above, performance levels, concentration and well-being are adversely affected at a concentration of 0.08% (800 ppm).
After just a few minutes, carbon dioxide levels reach 5,000 to 6,000 ppm in enclosed spaces like classrooms, offices or meeting rooms where people often congregate and which are subject to restricted ventilation. Theben CO₂ sensors measure CO₂ levels reliably. The measured values serve as an indicator for the ventilation control to increase the intake of fresh air.

Excursus: Max von Pettenkofer makes room air quality measurable

Max von Pettenkofer (3. December 1818 to 10. February 1901) was a professor of medical chemistry at the Ludwwig Maximilian University Munich and the first German professor of hygiene from 1865. With his studies on carbon dioxide levels 140 years ago, he laid the foundation for our current regulations relating to air quality (DIN-1946-2). This standard sets an upper CO₂ limit of 1,500 ppm. That means there should only be 1,500 CO₂ molecules per million air particles.

CO₂ level

Caption: Typical CO₂ levels (in ppm) and their affect on human beings.

1,000 ppm CO₂ – the threshold for good indoor air quality

Really good indoor air quality does not exceed a threshold of 1,000 ppm CO₂. Therefore, DIN 1946-6 requires an outdoor air flow of 30m³/h per person. A carbon dioxide level of 1,000 ppm CO₂ is not achievable by occasional ventilation or opening windows given modern building standards and the thickness of the outer shells of buildings. It is often the case that windows in public buildings such as schools, classrooms or large offices cannot be opened: Good indoor air quality can only be guaranteed in such cases by using a ventilation system controlled by a CO₂ sensor.

Application: CO₂ sensors in schools, offices, passive and low-energy houses

Due to statutory provisions a needs-driven input of fresh air to modern buildings such as passive and low-energy houses is essential to avoid health risks and damage to buildings over the long term. This is where Theben CO₂ sensors come into play: CO₂ sensors measure the relative humidity in buildings as well as CO₂ levels If set values are exceeded, CO₂ sensors such as AMUN 716 KNX send a signal to the building automation system, e.g. KNX, and the ventilation system draws in more fresh air or opens windows automatically. Conventional control is also possible with Theben CO2 sensors such as AMUN 716 R: It directly controls the ventilation system.

Ventilation control: CO₂ sensors for needs-driven ventilation control

Together with modern building systems technology such as KNX, CO₂ sensors make an enormous contribution to saving energy. Ventilation is a matter of guesswork without CO₂ sensors. And that's mostly too late or too much. Too much in this context means heat and heating costs are lost with the exchange of air. This is where Theben CO₂ sensors come to the fore: The readings of the CO₂ sensor show when, and for how long, ventilation is required. The ventilation system only introduces fresh air as long as it is actually required. In addition to the heating energy saved, speed-controlled ventilation via CO₂ sensors also offers large potential savings with fans in ventilation systems. The output of a fan depends on the third power of its speed. A reduction in speed of 20% leads to the halving of electricity consumption.

Volume flow

Caption: CO₂ sensors enable great potential savings in energy costs (green surface).

Measurement method: Non-dispersive infrared process

Theben CO₂ sensors measure CO₂ levels via infrared spectroscopy, also known as non-dispersive infrared process (NDIR). As CO₂ reduces the incidence of infrared light on the CO₂ sensor, the received signal changes in relation to the CO₂ levels in the indoor air.

Further information on Theben CO₂ sensors:

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During off-service hours you can contact our hotline: hotline@theben.de or fax to +49 (0)7474/692-207

Measure CO2 levels reliably with CO2 sensors

Contents:

Background: Increased CO2 levels and their consequences