Despite this, ventilation routines are rarely an issue in the workplace. Yet the limit values are regularly exceeded in almost every fifth office. We have measured with the air-Q how the CO₂ level can actually change through ventilation.
Why carbon dioxide as a ventilation indicator?
Carbon dioxide is the substance that increases most in unventilated rooms. The main cause is stale breathing air. If the CO₂ content of the air rises, we also automatically breathe faster and deeper and thus produce even more carbon dioxide.
Even low concentrations of over 1,000 ppm lead to poor concentration, performance deficits, malaise and even headaches. These symptoms occur long before the bad air is consciously perceived. From a CO₂ level of 1400 ppm, the air is already considered polluting, concentrations from 2000 ppm are classified as unacceptable. In rooms where many people are present, the levels quickly rise to 5000-6000 ppm. However, with an airtight construction and the associated low air exchange, the CO₂ level can quickly reach higher concentrations even with few people in the room.
The air quality before ventilation
But what is the benefit of ventilation in the workplace? We have done the test.
For the measurement, the air-Q was placed on the table in the middle of our 25m² office. The room was occupied by four people and equipped with two PCs and two laptops, all of which were in operation. The room temperature was 24 degrees Celsius while outside it measured 5 degrees Celsius. Since ventilation routines are still rare in many offices and there is often no air exchange, especially in the morning, the approx. 2.80 m high office was not yet ventilated for demonstration purposes on this day.
Before the window was opened at around 12:35 p.m., the CO₂ level (blue) was already at a critical level of 1700-1750 ppm and started to rise to just under 1800 ppm shortly before the window was opened. Corresponding to the critical CO₂ level, the performance index (red) was also at a very low level. For the calculation of the index, all substances are evaluated that have a direct impact on concentration and performance. The content and interaction of these elements are interpreted in the performance index and mapped to a value.
The CO₂ concentration during and after ventilation
At around 12:35 p.m., the office window was opened completely for shock ventilation. The air flowing in from outside was cold and naturally sank to the ground. As mixing of air masses generally takes place only gradually, there was no noticeable drop in the CO₂ level in the first few minutes after opening.
After about 5 minutes and more mixing of old air and fresh air, a significant drop in the CO₂ curve from just under 1800 ppm to 1400 ppm was already visible. After about 10 minutes, the level dropped further to around 1200 ppm. Correlating to this, the performance index rose very quickly to a significantly higher level.
Around 12:50 p.m., the window was closed again. A decrease in the carbon dioxide content could still be observed in the room - due to the further mixing of the air masses.
Conclusion: More efficient ventilation plans through regular air analysis
The surprising thing about the measurement - the CO₂ concentration changes surprisingly strongly through shock ventilation. The effect of efficient air exchange should therefore not be underestimated. It is generally recommended to ventilate every 2 hours. In the case of shock ventilation, about 5 minutes are sufficient, while air exchange via a tilted window can take up to an hour. Especially in winter, this leads to high energy consumption.
How strongly or quickly ventilation affects indoor air quality depends on several factors, such as the number of people, temperature, humidity, outside air, amount of technical equipment, size and height of the room or an energy-efficient, airtight design. In order to develop an effective ventilation routine according to the conditions on site, it is therefore important to know and monitor the individual room air precisely.
(Image: unsplash/ Tim van der Kuip)
