Background: Acute exposure to carbon dioxide could be caused diseases but in chronic exposure might be caused some mild to moderate symptoms and signs. Objective of this study was to determine the health effects of carbon dioxide in low to moderate concentration. Methods: The people who were employed in different industries were participated in this study. Groups were followed for brain and heart injury symptoms and signs. These groups were exposed to low concentrations of carbon dioxide; according to working sections, 4 groups were participated: working section A, working section B, working section C and working section D. Symptoms and signs were determined. Data were analyzed with SPSS 16.ANOVA, Chi-2, Exact test and relative risks with considering P<0.05 as significant level. Results: Working section D, had the most carbon dioxide concentration; 825.10±0.01 PPM. brain and heart injury symptoms and sign were determined. Loss of concentration, chest pain and headaches were the most in group D and relative risks were shown significant risks of carbon dioxide. Relative risks for loss of concentration was 2.25(1.34-3.77). Also relative risks for chest pain were 1.35(1.02-2.10). Conclusions: Carbon dioxide had health effects in low to moderate concentration and might be caused loss of concentration and chest pain.