Indoor Air Quality Measurement by Belimo

Humans spend around 90% of their lifetimes inside closed rooms, so a good room climate is important. Air quality in particular has a huge impact on our health and well-being. Air tight building shells may well be superior in terms of energy, but they prevent natural air exchange. However, they can be fully automated using appropriate ventilation systems and sensors.

The air around us comprises 21% oxygen, 78% nitrogen, 0.04% carbon dioxide (CO₂), as well as traces of noble gases, water vapour and pollutants. Today, one of the most important indicators of air quality in closed rooms is the CO₂ value. Because humans also produce CO₂ by breathing and add this to the air, the concentration of CO₂ continually increases in closed rooms where people are present. An air tight building shell means that the air exchange rate falls, resulting in an increased concentration of harmful substances in the indoor air. This can be counteracted by regularly venting rooms or, if this isn't possible, by fitting a ventilation system to take on this task. Because a ventilation system can also reliably remove air pollutants, it improves the air quality of rooms in which people are present over the long term. If such rooms are equipped with sensors, which provide the ventilation plant room with a permanent supply of data, the system will run in a reliable and independent manner.

Despite this, Figure 1 of the image below shows that CO₂ levels were found to be excessively high. In over 13% of the measurements taken at the end of the lesson, the CO₂ level was above 2000 ppm, which is the upper limit value for CO₂ concentrations in occupied rooms according to the SIA 180 standard. Figure 2 shows that the relative humidity was below 30% in a quarter of the measurements. This may result in health complications, such as a drying out of the airways' mucous membranes. Dust, dirt and germs are then not removed from the airways quickly enough. If these spend a long time in the respiratory tract, the risk of respiratory illnesses increases. Typical consequences include coughs, bronchitis, colds and sinus infections. The only good news is that from Figure 3 it can be seen that, with a few exceptions, the temperature in degrees Celsius was in an acceptable range.
 

Standardised guidelines exist for the composition of indoor air. To a great extent, these correspond to the feel-good factor. HVAC building automation is key to maintaining these. The ventilation plant room is networked with controllers and sensors. Air values in the rooms can be automatically optimised if the components that are fitted with sensors communicate reliable information to the plant room in order to control fans and regulate temperature, CO₂ content and air humidity. The building management technology then automatically compares the incoming information about the actual and nominal status in the room and gives the actuators the corresponding command to open or close dampers and valves or move them to an intermediate position. This enables the desired supply of air at a comfortable temperature, with the ideal level of humidity and a rich oxygen content.