(2011) for positive values (Z > 0) and p-value > 0.05. CUSUM test showed that Q magnitude did not exceed the critical value at 1% and 5% probability levels. Cumulative Sum Test (CUSUM) showed homogeneous and significant CO concentrations. Significant abrupt changes occurred in the months of May, June, July, August and September and insignificant in January, February, June, August and November at 1% and 5% probability. CO concentrations occurred in the predominant directions North-Northwest (NNW), South-Southwest (SSW) and South-west (SW). Both sectors are influenced by the main synoptic systems (Frontal System and South Atlantic Subtropical High) that act on CRJ. MK and CUSUM tests proved to be efficient in evaluating trends and abrupt changes in CO concentrations and air quality stations in the CRJ.