How to create your perfect environment?

27/08/2026 Esra Yunalova Seyfitinova

A modern ventilation system works completely autonomously. The most important parameters are continuously monitored in a discreet manner. Additional fresh air is supplied if one of the parameters deviates. No interaction from the residents is required for the proper functioning of the ventilation system. The system only provides an indication when maintenance is required. However, not every room in a building is used for the same purpose. Depending on the way a room is used, ventilation will have to be controlled differently. In this article we would like to discuss some typical situations for optimally controlling a ventilation system. The choice of sensor type is usually determined by the circumstances.

CO₂ sensors for spaces with variable occupancy
Indoor carbon dioxide concentrations are the result of a combination of outdoor CO₂, indoor breathing and the ventilation rate of the building. When people breathe, they release CO₂ into the air. If there's too much CO2, extra fresh air must be supplied to reduce the CO₂ level. As buildings and homes become more energy-efficient and thus airtight, this means we have less fresh air coming naturally into the building. Many of today’s ventilation systems recycle air to conserve energy, thus pushing contaminated air back into the building rather than cycling in new fresh air. This results in high CO₂ concentrations and poor indoor air quality. Air flow should be monitored to ensure fresh air is supplied in due time.

Moderate to high levels of carbon dioxide can cause headaches, reduced concentration and fatigue while higher concentrations can even produce nausea, dizziness and vomiting. Indoor CO₂ levels constantly change, depending on the ventilation, the amount of people and the length of time they are present in an enclosed space. Indoor CO₂ levels between 450 - 1.000 ppm are acceptable. When the values exceed this range, additional ventilation is required. Sentera CO₂ sensors accurately measure the CO₂ levels in the ambient air. They are available in different enclosure types, depending on the application.

In areas with variable occupancy such as meeting rooms, auditoriums or other rooms where many people periodically come together, there will be strong fluctuations in CO₂

concentration. Also in a living room or bedroom CO₂ sensors are the best choice to control a ventilation system and optimize the supply of fresh air. The CO₂ concentration must be measured in the extracted air. In residential environment, room or duct CO₂ sensors usually used for this application. In general we can assume that the CO₂ level of the supplied air is quite constant and in all cases is lower than the CO₂ level of the indoor air. Other parameters such as relative humidity and VOC concentrations usually remain more stable in these spaces.

If the rooms in the building are equipped with control valves to regulate the amount of supplied air and the amount of extracted air, the exhaust valve should be controlled by a CO₂ controller in the room. The supply valve should follow the position of the exhaust valve to avoid over pressure or under pressure in the room (balanced ventilation). If there is only one central exhaust fan or one heat recovery unit, it can be directly controlled by the CO₂ controller. Another option is to install multiple sensors and to control ventilation based on the highest CO₂ measurement in the building. For this purpose, Sentera developed the solution FS-D-000064.

To control the ventilation system not only on the basis of the CO₂ measurement, but on the basis of both CO₂ and relative humidity (and possibly also temperature), a CO₂ controller must be used. This device has a built-in control algorithm that can control a valve or fan speed. All (or some) of the measured values will be taken into account by the algorithm.

A CO₂ sensor converts the measured CO₂ value as well as the relative humidity (and temperature) into three separate analog signals. A valve position or fan speed can be controlled with one of these signals. Not with all three at the same time.

Prevent condensation in wet rooms

Spaces such as toilets, bathrooms or kitchens have greater variations in relative humidity. Relative humidity indicates the actual water content of air as a percentage of the maximum amount it could possibly hold at its current temperature. Warm air can possess more water moisture than cold air, so with the same amount of absolute/specific humidity, the relative humidity of cold air would be far higher than of warm air. Other parameters such as CO₂ or VOC generally remain more constant here. It therefore makes more sense to ventilate these areas in such a way that the risk of condensation is minimized. Condensation or excessive humidity can lead to mold and mildew, which isn't good for anyone's health.

Controlling the ventilation system based on the relative humidity in the room itself is not effective. The relative humidity of the supplied air will also not be constant. When controlling the ventilation system based on CO₂, it can be assumed that the CO₂ concentration of fresh outside air is fairly constant. That is not the case with relative humidity. The relative humidity outside on a warm summer day or a wet autumn day will be completely different. Regulating a ventilation system only on the relative humidity measurement inside, doesn’t work.

Based on the temperature and relative humidity measurements, the dew point temperature can be calculated. Sentera relative humidity sensors measure both temperature and relative humidity and automatically calculate the dew point temperature. When the air comes into contact with an object that has a temperature lower than the dew point temperature, condensation occurs. So, the dew point temperature of the supplied air must always be lower than the temperature inside the wet room. When we obtain this, we can avoid condensation.

So when the relative humidity in a wet room is too high, this can be solved by ventilation if the dew point temperature of the supplied air is sufficiently low. This requires a relative humidity sensor in the interior space as well as a dew point temperature calculation of the supplied air.

VOC Sensors in Rooms with Specific Destinations

Some rooms require more than CO₂ or humidity monitoring to maintain good indoor air quality. VOC sensors are particularly useful in spaces where specific activities, materials or products can release volatile organic compounds (VOCs) into the air.

VOCs can be released by paints, varnishes, adhesives, cleaning products, furniture and building materials, as well as by activities such as printing, photocopying, smoking or burning wood. Elevated VOC levels can negatively affect indoor air quality and may cause discomfort such as headaches, tiredness, irritation and reduced concentration. Good ventilation is therefore especially important in areas where these sources are present.

VOC monitoring is particularly suitable for storage rooms, rooms with photocopiers or printing equipment, printing facilities, workshops and warehouses for building materials. In these spaces, the sensor continuously monitors changes in air quality and allows the ventilation system to react when needed. When VOC levels increase, the ventilation can increase the airflow to remove polluted air more quickly. When the air quality improves, the system can reduce the airflow again.

This approach is especially useful when CO₂ or humidity monitoring alone is not enough. CO₂ is mainly an indicator of occupancy, while VOC monitoring can detect changes caused by materials, products and specific activities. This gives the ventilation system additional information and allows it to respond more effectively to the actual conditions in the room.

The DSVCG2-4 is designed for air quality monitoring in ventilation ducts. It measures temperature, relative humidity and VOC Index, providing a clear indication of changes in air quality. The VOC Index can be used to support demand-controlled ventilation and determine when additional airflow is required.

The sensor can be integrated into supply, exhaust and balanced ventilation systems, as well as ventilation controllers and building management systems. In a balanced system, the exhaust airflow can respond to the VOC level while the supply airflow follows accordingly. This helps maintain a stable indoor environment and prevents unwanted pressure differences between the room and surrounding spaces.

By continuously monitoring air quality and adjusting ventilation when necessary, the DSVCG2-4 can help create a cleaner, more comfortable and healthier indoor environment. At the same time, ventilation is only increased when the measured conditions require it, helping avoid unnecessary airflow and energy consumption.