The aim of the present study is to determine the effect of yucca (Yucca elephantipes Regel), dieffenbachia (Dieffenbachia amoena Gentil), and spathiphyllum (Spathiphyllum floribundum Schott) as common types of indoor plants on CO₂ levels in the environment. The study was conducted in a closed environment where air inlet/outlet was absent. As a result, the plants were found to affect the level of CO₂ in the environment to different extents; and while Dieffenbachia began to respire at around 13:00 hrs, yucca and spathiphyllum continued to photosynthesize until 19:00. While dieffenbachia and spathiphyllum could not lower the CO₂ level in the environment to below 500 ppm, yucca could decrease it to 475 ppm in a day. The results of the study demonstrated that CO₂ levels in photosynthesis during the day were 8.3, 5.8, and 1.4 times more in yucca, spathiphyllum, and dieffenbachia, respectively, in comparison with CO₂ levels released through respiration.