Nowadays an importance of indoor air quality is highlighted by numerous researches. There are strong dependence between CO2 concentration and human health and office workers performance. This study provides research on sportsmen performance under different indoor air parameters. During the study the IAQ parameters were measured in three different sport halls and special questionnaires were distributed between taekwondo sportsmen. Age of sportsmen 10 – 15 years. In order to evaluate performance of taekwondo fighters the total number of received scores by the same fighters in different sport halls were compared. Results have shown that in sport hall with higher CO2 concentration number of received scores were much smaller in comparison to halls with CO2 concentration at 1000ppm.