There are more than 200 thousand pupils in Latvia. Most of them are still learning in non-renovated classrooms without proper mechanical ventilation. The classrooms are often ventilated only during the breaks by opening windows. This can lead to increased CO₂ levels and reduced mental performance. To test how CO₂ concentration in classrooms influences student attention level and their ability to perform mental tasks, the students had to complete a short test at the start and the end of the class. At the same time CO₂ concentration, temperature and relative humidity were logged. In addition, an anonymous survey on how the pupils felt regarding the overall indoor environmental quality (IEQ) in the classroom, their thermal sensation, are they fatigued, any difficulty concentrating and if they have headaches during the lesson performed. The measurements were performed in a Secondary School in Daugavpils, Latvia. The analysis of results shows that existing 10 min breaks are not enough to fully ventilate the classroom, and they must be increased to at least 15 min. At the same time, 30 min breaks can be reduced to 20 min. The correlation between CO₂ concentration and test results of pupils’ performance test results is noticeable but not definitive. It indicates that at increased CO₂ levels the performance lowers—when the concentration of CO₂ corresponds only to the Category 3 norm, the lowest results are achieved while the best results are when the CO₂ concentration level corresponds to Category 1. To improve the study, observations of CO₂ concentrations must be extended throughout the school year, as well as measurements in other classrooms in the school should be made.

The COVID-19 crisis has affected the process of how the study procedures are organized at schools in Latvia. Three different options were available for the school to choose from. However, most schools have opted for option A which states that the classes are organized face-to-face but various safety measures must be ensured. Each class or group is equated to a closed set where there are no distance requirements. In turn, the distance between the classes must be observed. This means that students stay in the same class all day and are accompanied by teachers of the respective classes. This can lead to improper ventilation as for most of the schools in Latvia it is organized through the opening of windows. To test this, measurements of CO₂ concentration were done in a classroom Secondary School in Daugavpils. The results showed that the CO₂ concentration was very high and often reached and exceeded the maximum measuring capacity of the device - 4000 ppm. It indicates that following the special safety procedures cause a negative effect on IAQ as the classrooms are not properly ventilated. This can lead to a drop in the performance of pupils as well as stimulate the transmission of other infectious diseases. Further measurements are necessary to gather data from different schools and best practices must be found.

As energy consumption for building engineering systems is a major part of the total energy spent, it is necessary to reduce it. This leads to the need for the development of new solutions for the control of heating, ventilation, and conditioning (HVAC) systems that are responsive to humans and their demands. In this review article, the existing research and technology advancements of the modern technologies of computer vision and neural networks for application in HVAC control systems are studied. Objectives such as human detection and location, human activity monitoring, skin temperature detection, and clothing level detection systems are important for the operation of precise, high-tech HVAC systems. This article tries to compile the latest achievements and principal solutions on how this information is acquired. Moreover, it how parameters such as indoor air quality (IAQ), variable air volume ventilation, computer vision, metabolic rate, and human clothing isolation can affect final energy consumption is studied. The research studies discussed in this review article have been tested in real application scenarios and prove the benefits of using a particular technology in ventilation systems. As a result, the modernized control systems have shown advantages over the currently applied typical non-automated systems by providing higher IAQ and reducing unnecessary energy consumption.