In traffic congestions, the typical reaction of the drivers is to switch-on the recirculation mode of the vehicle's air conditioning system. In the summertime, in many cities with high air humidity and temperatures, people typically drive their cars in recirculation mode as well, to ensure the best cooling. However, the recirculation mode of the air in the cabin prevents O 2 from entering and leads to an increase in CO 2. In confined spaces (e.g., a vehicle cabin), the raised CO 2 concentration due to human exhalation and metabolism is associated with increased health symptoms, decreased concentration, and impaired performance. The paper presents an experimental study on the accumulation of carbon dioxide in a vehicle cabin from occupants breathing and metabolism. The concentration of CO 2 and O 2 were measured in terms of the number of occupants (1-4) in the car. The change in the indoor environmental parameters in the car cabin was also monitored. The results obtained show the increment of the CO 2 concentration at the expense of oxygen availability, together with the apparent impact of the number of people in the vehicle.

The study presents experiments, conducted with human subjects in an artificial cold chamber, assessing the influence of a cold environment on the temperature of the human body. Infrared thermography was applied as a non-invasive, contactless method for direct measurement of the temperature distribution of both clothed and uncovered parts of the body. Two subzero temperatures were applied and clothing ensembles with two different clothing insulation values were used to assess the effect of the clothing insulation of the torso on the temperature of clothed and uncovered parts of the body of the participants. The average temperature of the chest, back, upper arms, face and middle finger is presented and discussed in relation to the cold exposure duration and clothing insulation used. The results obtained showed the strong influence of the clothing insulation over the torso on skin and clothing temperatures of the body and overall cooling of the body in subzero temperatures.

The pyrolysis of wheat straw in order to produce biochar for soil amendment is a potential strategy for producing environmental friendly fertilizers capable of boosting soil fertility, increasing carbon storage, and lowering greenhouse gas emissions. However, straw biochar’s potential to influence these aspects may vary depending on its properties. Our study sought to investigate biochar from wheat straw from three different regions in Bulgaria. A specially designed set up was used for the biochar production. Three pyrolytic temperatures (300, 400, and 500 °C) were applied, resulting in nine biochar samples. The specific characteristics included moisture content, volatile substances content, ash content, fixed carbon content, and joint ash and carbon content, and they were determined for each sample. The chemical content, resulting in 17 chemical elements and compounds, was measured and analysed. The results obtained showed that the produced straw biochar has the potential to be used as a fertilizer and soil supplement.

The objective of the paper is to demonstrate the importance of the unsteady Computational Fluid Dynamics (CFD) simulations and long-term measurements for the reliable assessment of thermal comfort indoors, for proper categorization of the indoor thermal environment and for identifying the reasons for complaints due to draught discomfort. Numerical simulations and experimental measurements were applied in combination to study ventilation in a field laboratory, a university classroom with a controlled indoor environment. Strong unsteadiness of the airflow was registered both in the unsteady RANS results and the real-scale long-term velocity data measured with thermo anemometer. Low-frequency high-amplitude velocity fluctuations observed lead to substantial time variation of the draught rate. In case of categorization of a thermal environment, the point measurements or steady-state RANS computations would lead to wrong conclusions as well as they cannot be used for identification of the reasons for people’s complaints due to draught discomfort if strong unsteadiness of the airflow exists. It is demonstrated that the length of the time interval for draught rate (DR) assessment may not be universal if low-frequency high-amplitude pulsations are present in the room airflow.