## 2 Factors Affecting Indoor Air Quality in Educational Centers  
As an integral aspect of the educational journey, students commonly enrol in elementary, middle, and high schools, devoting a substantial portion of their day to classroom instructions [24]. Investigations into classroom air quality and student responses have indicated a strong link between air quality and students' attention processes, with high levels of CO\({}_{2}\) concentration leading to reduced attention span and decision-making abilities among students [25; 26; 27]. Beyond investigations concerning CO\({}_{2}\) concentration and its effects on occupants' well-being, findings from several researchers have indicated that, in practical terms, CO\({}_{2}\) concentration can serve as a proxy for IAQ acceptability [6; 9; 22; 28; 29],the appropriateness of air exchange, and whether sufficient fresh air is being introduced into indoor environments [28; 30].  
Prior research on CO\({}_{2}\) levels within indoor spaces has highlighted several key factors as influential variables. These include (1) the CO\({}_{2}\) generation rate; (2) the outdoor CO\({}_{2}\) concentrations; (3) the volume flow rate; (4) the room dimensions, and (5) the number of occupants within a given space.  
While numerous studies have explored CO\({}_{2}\) generation rates in adults under various activity levels, there is limited research focused specifically on children and adolescents during typical educational activities. Obtaining accurate CO\({}_{2}\) generation data for younger age groups from existing standards or literature can be challenging. Age plays a significant role in CO\({}_{2}\) production, with notable sex-related differences emerging after the age of 15--at which point boys tend to produce significantly more CO\({}_{2}\) than girls.  
In general, CO\({}_{2}\) generation increases proportionally with physical activity levels across all age groups. However, due to differences in body size and metabolic rates, children--particularly those between 5 and 12 years of age--consistently generate less CO\({}_{2}\) than adults performing the same activities [31].  
CO\({}_{2}\) emissions from outdoors sources may also have immediate implications for the indoor environment [32; 33; 34], since the air in both naturally and mechanically ventilated buildings is replenished to varying degrees with ambient air, which may or may not be filtered or otherwise conditioned before being brought indoors.  
Although elevated CO\({}_{2}\) levels alone might negatively impact students' alertness and concentration [35], CO\({}_{2}\) is not classified as a pollutant by the World Health Organization. Indoor air quality in schools is negatively affected by several pollutants that are the result of physical, chemical and biological factors along with the adequacy of ventilation in the environment [36].  
Aside from the indoor generation rate and outdoors concentrations incomes, IAQ is also influenced by a multitude of additional factors, such as the size and layout of the classroom, including its area, volume and ceiling height. These factors, in turn, have a strong relationship with a number of occupants and density per floor area and cubic meter, activity and exposure time, window type (openable area and glazing), the airtightness of the building envelope, exposure to wind direction, and ventilation strategy.  
As a result, IAQ is influenced by a multitude of factors, making its management and control crucial for maintaining optimal conditions. Therefore, introducing a Simplified Classroom Indoor Air Quality Risk Index based on the above listed factors could signify progress in both the design and management of educational indoor environments.